cgroup.c 142.6 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 33
#include <linux/errno.h>
#include <linux/fs.h>
34
#include <linux/init_task.h>
35 36 37 38 39 40
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
41
#include <linux/proc_fs.h>
42 43
#include <linux/rcupdate.h>
#include <linux/sched.h>
44
#include <linux/backing-dev.h>
45 46 47 48 49
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
50
#include <linux/sort.h>
51
#include <linux/kmod.h>
52
#include <linux/module.h>
B
Balbir Singh 已提交
53 54
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
55
#include <linux/hash.h>
56
#include <linux/namei.h>
L
Li Zefan 已提交
57
#include <linux/pid_namespace.h>
58
#include <linux/idr.h>
59
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
60 61
#include <linux/eventfd.h>
#include <linux/poll.h>
62
#include <linux/flex_array.h> /* used in cgroup_attach_proc */
63
#include <linux/kthread.h>
B
Balbir Singh 已提交
64

A
Arun Sharma 已提交
65
#include <linux/atomic.h>
66

67 68 69
/* css deactivation bias, makes css->refcnt negative to deny new trygets */
#define CSS_DEACT_BIAS		INT_MIN

T
Tejun Heo 已提交
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
/*
 * 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.
 */
86
static DEFINE_MUTEX(cgroup_mutex);
T
Tejun Heo 已提交
87
static DEFINE_MUTEX(cgroup_root_mutex);
88

B
Ben Blum 已提交
89 90 91 92 93 94
/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
95
#define SUBSYS(_x) &_x ## _subsys,
B
Ben Blum 已提交
96
static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
97 98 99
#include <linux/cgroup_subsys.h>
};

100 101
#define MAX_CGROUP_ROOT_NAMELEN 64

102 103 104 105 106 107 108 109 110 111 112 113 114 115
/*
 * A cgroupfs_root represents the root of a cgroup hierarchy,
 * and may be associated with a superblock to form an active
 * hierarchy
 */
struct cgroupfs_root {
	struct super_block *sb;

	/*
	 * The bitmask of subsystems intended to be attached to this
	 * hierarchy
	 */
	unsigned long subsys_bits;

116 117 118
	/* Unique id for this hierarchy. */
	int hierarchy_id;

119 120 121 122 123 124 125 126 127 128 129 130
	/* The bitmask of subsystems currently attached to this hierarchy */
	unsigned long actual_subsys_bits;

	/* A list running through the attached subsystems */
	struct list_head subsys_list;

	/* The root cgroup for this hierarchy */
	struct cgroup top_cgroup;

	/* Tracks how many cgroups are currently defined in hierarchy.*/
	int number_of_cgroups;

131
	/* A list running through the active hierarchies */
132 133
	struct list_head root_list;

134 135 136
	/* All cgroups on this root, cgroup_mutex protected */
	struct list_head allcg_list;

137 138
	/* Hierarchy-specific flags */
	unsigned long flags;
139

140
	/* The path to use for release notifications. */
141
	char release_agent_path[PATH_MAX];
142 143 144

	/* The name for this hierarchy - may be empty */
	char name[MAX_CGROUP_ROOT_NAMELEN];
145 146 147 148 149 150 151 152 153
};

/*
 * 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
154 155 156 157 158 159 160 161 162
/*
 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 */
struct cfent {
	struct list_head		node;
	struct dentry			*dentry;
	struct cftype			*type;
};

K
KAMEZAWA Hiroyuki 已提交
163 164 165 166 167 168 169 170 171 172
/*
 * 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
173 174
	 * is called after synchronize_rcu(). But for safe use, css_tryget()
	 * should be used for avoiding race.
K
KAMEZAWA Hiroyuki 已提交
175
	 */
A
Arnd Bergmann 已提交
176
	struct cgroup_subsys_state __rcu *css;
K
KAMEZAWA Hiroyuki 已提交
177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194
	/*
	 * 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) */
};

195
/*
L
Lucas De Marchi 已提交
196
 * cgroup_event represents events which userspace want to receive.
197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223
 */
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
224

225 226 227
/* The list of hierarchy roots */

static LIST_HEAD(roots);
228
static int root_count;
229

230 231 232 233
static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
static DEFINE_SPINLOCK(hierarchy_id_lock);

234 235 236 237
/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)

/* This flag indicates whether tasks in the fork and exit paths should
L
Li Zefan 已提交
238 239 240
 * 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.
241
 */
242
static int need_forkexit_callback __read_mostly;
243

244 245 246 247 248 249 250 251 252 253 254 255 256 257
#ifdef CONFIG_PROVE_LOCKING
int cgroup_lock_is_held(void)
{
	return lockdep_is_held(&cgroup_mutex);
}
#else /* #ifdef CONFIG_PROVE_LOCKING */
int cgroup_lock_is_held(void)
{
	return mutex_is_locked(&cgroup_mutex);
}
#endif /* #else #ifdef CONFIG_PROVE_LOCKING */

EXPORT_SYMBOL_GPL(cgroup_lock_is_held);

258 259 260 261 262
static int css_unbias_refcnt(int refcnt)
{
	return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
}

263 264 265 266 267
/* 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);

268
	return css_unbias_refcnt(v);
269 270
}

271
/* convenient tests for these bits */
272
inline int cgroup_is_removed(const struct cgroup *cgrp)
273
{
274
	return test_bit(CGRP_REMOVED, &cgrp->flags);
275 276 277 278 279 280 281
}

/* bits in struct cgroupfs_root flags field */
enum {
	ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};

282
static int cgroup_is_releasable(const struct cgroup *cgrp)
283 284
{
	const int bits =
285 286 287
		(1 << CGRP_RELEASABLE) |
		(1 << CGRP_NOTIFY_ON_RELEASE);
	return (cgrp->flags & bits) == bits;
288 289
}

290
static int notify_on_release(const struct cgroup *cgrp)
291
{
292
	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
293 294
}

295 296 297 298 299
static int clone_children(const struct cgroup *cgrp)
{
	return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
}

300 301 302 303 304 305 306
/*
 * 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)

307 308
/* for_each_active_root() allows you to iterate across the active hierarchies */
#define for_each_active_root(_root) \
309 310
list_for_each_entry(_root, &roots, root_list)

311 312 313 314 315
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

T
Tejun Heo 已提交
316
static inline struct cfent *__d_cfe(struct dentry *dentry)
317 318 319 320
{
	return dentry->d_fsdata;
}

T
Tejun Heo 已提交
321 322 323 324 325
static inline struct cftype *__d_cft(struct dentry *dentry)
{
	return __d_cfe(dentry)->type;
}

326 327 328
/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
329
static DEFINE_RAW_SPINLOCK(release_list_lock);
330 331
static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
332
static void check_for_release(struct cgroup *cgrp);
333

334 335 336 337 338 339
/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
	/*
	 * List running through cg_cgroup_links associated with a
	 * cgroup, anchored on cgroup->css_sets
	 */
340
	struct list_head cgrp_link_list;
341
	struct cgroup *cgrp;
342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359
	/*
	 * List running through cg_cgroup_links pointing at a
	 * single css_set object, anchored on css_set->cg_links
	 */
	struct list_head cg_link_list;
	struct css_set *cg;
};

/* 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;
static struct cg_cgroup_link init_css_set_link;

360 361
static int cgroup_init_idr(struct cgroup_subsys *ss,
			   struct cgroup_subsys_state *css);
K
KAMEZAWA Hiroyuki 已提交
362

363 364 365 366 367 368
/* 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;

369 370 371 372 373
/*
 * 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.
 */
374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392
#define CSS_SET_HASH_BITS	7
#define CSS_SET_TABLE_SIZE	(1 << CSS_SET_HASH_BITS)
static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];

static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
{
	int i;
	int index;
	unsigned long tmp = 0UL;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
		tmp += (unsigned long)css[i];
	tmp = (tmp >> 16) ^ tmp;

	index = hash_long(tmp, CSS_SET_HASH_BITS);

	return &css_set_table[index];
}

393 394 395 396
/* 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 */
397
static int use_task_css_set_links __read_mostly;
398

399
static void __put_css_set(struct css_set *cg, int taskexit)
400
{
K
KOSAKI Motohiro 已提交
401 402
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
403 404 405 406 407 408 409 410 411 412 413 414
	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
	if (atomic_add_unless(&cg->refcount, -1, 1))
		return;
	write_lock(&css_set_lock);
	if (!atomic_dec_and_test(&cg->refcount)) {
		write_unlock(&css_set_lock);
		return;
	}
415

416 417 418 419 420 421 422 423 424
	/* This css_set is dead. unlink it and release cgroup refcounts */
	hlist_del(&cg->hlist);
	css_set_count--;

	list_for_each_entry_safe(link, saved_link, &cg->cg_links,
				 cg_link_list) {
		struct cgroup *cgrp = link->cgrp;
		list_del(&link->cg_link_list);
		list_del(&link->cgrp_link_list);
425 426
		if (atomic_dec_and_test(&cgrp->count) &&
		    notify_on_release(cgrp)) {
427
			if (taskexit)
428 429
				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
430
		}
431 432

		kfree(link);
433
	}
434 435

	write_unlock(&css_set_lock);
436
	kfree_rcu(cg, rcu_head);
437 438
}

439 440 441 442 443
/*
 * refcounted get/put for css_set objects
 */
static inline void get_css_set(struct css_set *cg)
{
444
	atomic_inc(&cg->refcount);
445 446 447 448
}

static inline void put_css_set(struct css_set *cg)
{
449
	__put_css_set(cg, 0);
450 451
}

452 453
static inline void put_css_set_taskexit(struct css_set *cg)
{
454
	__put_css_set(cg, 1);
455 456
}

457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528
/*
 * compare_css_sets - helper function for find_existing_css_set().
 * @cg: candidate css_set being tested
 * @old_cg: existing css_set for a task
 * @new_cgrp: cgroup that's being entered by the task
 * @template: desired set of css pointers in css_set (pre-calculated)
 *
 * Returns true if "cg" matches "old_cg" except for the hierarchy
 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 */
static bool compare_css_sets(struct css_set *cg,
			     struct css_set *old_cg,
			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

	if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
		/* 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.
	 */

	l1 = &cg->cg_links;
	l2 = &old_cg->cg_links;
	while (1) {
		struct cg_cgroup_link *cgl1, *cgl2;
		struct cgroup *cg1, *cg2;

		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
		if (l1 == &cg->cg_links) {
			BUG_ON(l2 != &old_cg->cg_links);
			break;
		} else {
			BUG_ON(l2 == &old_cg->cg_links);
		}
		/* Locate the cgroups associated with these links. */
		cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
		cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
		cg1 = cgl1->cgrp;
		cg2 = cgl2->cgrp;
		/* Hierarchies should be linked in the same order. */
		BUG_ON(cg1->root != cg2->root);

		/*
		 * If this hierarchy is the hierarchy of the cgroup
		 * that's changing, then we need to check that this
		 * css_set points to the new cgroup; if it's any other
		 * hierarchy, then this css_set should point to the
		 * same cgroup as the old css_set.
		 */
		if (cg1->root == new_cgrp->root) {
			if (cg1 != new_cgrp)
				return false;
		} else {
			if (cg1 != cg2)
				return false;
		}
	}
	return true;
}

529 530 531
/*
 * find_existing_css_set() is a helper for
 * find_css_set(), and checks to see whether an existing
532
 * css_set is suitable.
533 534 535 536
 *
 * oldcg: the cgroup group that we're using before the cgroup
 * transition
 *
537
 * cgrp: the cgroup that we're moving into
538 539 540 541 542 543
 *
 * template: location in which to build the desired set of subsystem
 * state objects for the new cgroup group
 */
static struct css_set *find_existing_css_set(
	struct css_set *oldcg,
544
	struct cgroup *cgrp,
545
	struct cgroup_subsys_state *template[])
546 547
{
	int i;
548
	struct cgroupfs_root *root = cgrp->root;
549 550 551
	struct hlist_head *hhead;
	struct hlist_node *node;
	struct css_set *cg;
552

B
Ben Blum 已提交
553 554 555 556 557
	/*
	 * 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.
	 */
558
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
559
		if (root->subsys_bits & (1UL << i)) {
560 561 562
			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
563
			template[i] = cgrp->subsys[i];
564 565 566 567 568 569 570
		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
			template[i] = oldcg->subsys[i];
		}
	}

571 572
	hhead = css_set_hash(template);
	hlist_for_each_entry(cg, node, hhead, hlist) {
573 574 575 576 577
		if (!compare_css_sets(cg, oldcg, cgrp, template))
			continue;

		/* This css_set matches what we need */
		return cg;
578
	}
579 580 581 582 583

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

584 585 586 587 588 589 590 591 592 593 594
static void free_cg_links(struct list_head *tmp)
{
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;

	list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
		list_del(&link->cgrp_link_list);
		kfree(link);
	}
}

595 596
/*
 * allocate_cg_links() allocates "count" cg_cgroup_link structures
597
 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
598 599 600 601 602 603 604 605 606 607
 * success or a negative error
 */
static int allocate_cg_links(int count, struct list_head *tmp)
{
	struct cg_cgroup_link *link;
	int i;
	INIT_LIST_HEAD(tmp);
	for (i = 0; i < count; i++) {
		link = kmalloc(sizeof(*link), GFP_KERNEL);
		if (!link) {
608
			free_cg_links(tmp);
609 610
			return -ENOMEM;
		}
611
		list_add(&link->cgrp_link_list, tmp);
612 613 614 615
	}
	return 0;
}

616 617 618 619 620 621 622 623 624 625 626 627 628 629 630
/**
 * link_css_set - a helper function to link a css_set to a cgroup
 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
 * @cg: the css_set to be linked
 * @cgrp: the destination cgroup
 */
static void link_css_set(struct list_head *tmp_cg_links,
			 struct css_set *cg, struct cgroup *cgrp)
{
	struct cg_cgroup_link *link;

	BUG_ON(list_empty(tmp_cg_links));
	link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
				cgrp_link_list);
	link->cg = cg;
631
	link->cgrp = cgrp;
632
	atomic_inc(&cgrp->count);
633
	list_move(&link->cgrp_link_list, &cgrp->css_sets);
634 635 636 637 638
	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
	list_add_tail(&link->cg_link_list, &cg->cg_links);
639 640
}

641 642 643 644 645 646 647 648
/*
 * 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
 */
static struct css_set *find_css_set(
649
	struct css_set *oldcg, struct cgroup *cgrp)
650 651 652 653 654 655
{
	struct css_set *res;
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	struct list_head tmp_cg_links;

656
	struct hlist_head *hhead;
657
	struct cg_cgroup_link *link;
658

659 660
	/* First see if we already have a cgroup group that matches
	 * the desired set */
661
	read_lock(&css_set_lock);
662
	res = find_existing_css_set(oldcg, cgrp, template);
663 664
	if (res)
		get_css_set(res);
665
	read_unlock(&css_set_lock);
666 667 668 669 670 671 672 673 674 675 676 677 678 679

	if (res)
		return res;

	res = kmalloc(sizeof(*res), GFP_KERNEL);
	if (!res)
		return NULL;

	/* Allocate all the cg_cgroup_link objects that we'll need */
	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
		kfree(res);
		return NULL;
	}

680
	atomic_set(&res->refcount, 1);
681 682
	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
683
	INIT_HLIST_NODE(&res->hlist);
684 685 686 687 688 689 690

	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
	memcpy(res->subsys, template, sizeof(res->subsys));

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
691 692 693 694 695 696
	list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
		struct cgroup *c = link->cgrp;
		if (c->root == cgrp->root)
			c = cgrp;
		link_css_set(&tmp_cg_links, res, c);
	}
697 698 699 700

	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
701 702 703 704 705

	/* Add this cgroup group to the hash table */
	hhead = css_set_hash(res->subsys);
	hlist_add_head(&res->hlist, hhead);

706 707 708
	write_unlock(&css_set_lock);

	return res;
709 710
}

711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745
/*
 * 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)
{
	struct css_set *css;
	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.
	 */
	css = task->cgroups;
	if (css == &init_css_set) {
		res = &root->top_cgroup;
	} else {
		struct cg_cgroup_link *link;
		list_for_each_entry(link, &css->cg_links, cg_link_list) {
			struct cgroup *c = link->cgrp;
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

746 747 748 749 750 751 752 753 754 755
/*
 * 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
756
 * cgroup_attach_task() can increment it again.  Because a count of zero
757 758 759 760 761 762 763 764 765 766 767 768 769
 * 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
770 771
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
772 773 774 775 776 777 778 779 780 781 782
 *
 * 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
783
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
Li Zefan 已提交
784
 * another.  It does so using cgroup_mutex, however there are
785 786 787
 * 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
788
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
789 790 791 792
 * 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
793
 * update of a tasks cgroup pointer by cgroup_attach_task()
794 795 796 797 798 799 800 801 802 803
 */

/**
 * cgroup_lock - lock out any changes to cgroup structures
 *
 */
void cgroup_lock(void)
{
	mutex_lock(&cgroup_mutex);
}
B
Ben Blum 已提交
804
EXPORT_SYMBOL_GPL(cgroup_lock);
805 806 807 808 809 810 811 812 813 814

/**
 * cgroup_unlock - release lock on cgroup changes
 *
 * Undo the lock taken in a previous cgroup_lock() call.
 */
void cgroup_unlock(void)
{
	mutex_unlock(&cgroup_mutex);
}
B
Ben Blum 已提交
815
EXPORT_SYMBOL_GPL(cgroup_unlock);
816 817 818 819 820 821 822 823

/*
 * 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.
 */

824
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
A
Al Viro 已提交
825
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
826
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
827
static int cgroup_populate_dir(struct cgroup *cgrp);
828
static const struct inode_operations cgroup_dir_inode_operations;
829
static const struct file_operations proc_cgroupstats_operations;
830 831

static struct backing_dev_info cgroup_backing_dev_info = {
832
	.name		= "cgroup",
833
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
834
};
835

K
KAMEZAWA Hiroyuki 已提交
836 837 838
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

A
Al Viro 已提交
839
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
840 841 842 843
{
	struct inode *inode = new_inode(sb);

	if (inode) {
844
		inode->i_ino = get_next_ino();
845
		inode->i_mode = mode;
846 847
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
848 849 850 851 852 853
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

854 855 856 857
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
858
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
859 860
{
	struct cgroup_subsys *ss;
861 862
	int ret = 0;

863 864 865 866 867
	for_each_subsys(cgrp->root, ss) {
		if (!ss->pre_destroy)
			continue;

		ret = ss->pre_destroy(cgrp);
868
		if (WARN_ON_ONCE(ret))
869 870
			break;
	}
871

872
	return ret;
873 874
}

875 876 877 878
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)) {
879
		struct cgroup *cgrp = dentry->d_fsdata;
880
		struct cgroup_subsys *ss;
881
		BUG_ON(!(cgroup_is_removed(cgrp)));
882 883 884 885 886 887 888
		/* It's possible for external users to be holding css
		 * reference counts on a cgroup; css_put() needs to
		 * be able to access the cgroup after decrementing
		 * the reference count in order to know if it needs to
		 * queue the cgroup to be handled by the release
		 * agent */
		synchronize_rcu();
889 890 891 892 893

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
894
		for_each_subsys(cgrp->root, ss)
895
			ss->destroy(cgrp);
896 897 898 899

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

900
		/*
901 902
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
903
		 */
904
		deactivate_super(cgrp->root->sb);
905

906 907 908 909 910 911
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

912
		kfree_rcu(cgrp, rcu_head);
T
Tejun Heo 已提交
913 914 915 916 917 918 919 920
	} 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);
		kfree(cfe);
921 922 923 924
	}
	iput(inode);
}

925 926 927 928 929
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

930 931 932 933 934 935 936 937 938
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);
}

T
Tejun Heo 已提交
939 940 941 942 943 944 945 946 947 948 949 950 951 952 953
static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
{
	struct cfent *cfe;

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

	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

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

		dget(d);
		d_delete(d);
954
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
955 956 957 958
		list_del_init(&cfe->node);
		dput(d);

		return 0;
959
	}
T
Tejun Heo 已提交
960 961 962 963 964 965 966 967 968
	return -ENOENT;
}

static void cgroup_clear_directory(struct dentry *dir)
{
	struct cgroup *cgrp = __d_cgrp(dir);

	while (!list_empty(&cgrp->files))
		cgroup_rm_file(cgrp, NULL);
969 970 971 972 973 974 975
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
976 977
	struct dentry *parent;

978 979
	cgroup_clear_directory(dentry);

N
Nick Piggin 已提交
980 981
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
982
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
983
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
984 985
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
986 987 988
	remove_dir(dentry);
}

989 990 991 992 993 994
/*
 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
 * reference to css->refcnt. In general, this refcnt is expected to goes down
 * to zero, soon.
 *
995
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
996
 */
997
static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
998

999
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
1000
{
1001
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
1002 1003 1004
		wake_up_all(&cgroup_rmdir_waitq);
}

1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
{
	css_get(css);
}

void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
{
	cgroup_wakeup_rmdir_waiter(css->cgroup);
	css_put(css);
}

B
Ben Blum 已提交
1016
/*
B
Ben Blum 已提交
1017 1018 1019
 * 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
1020
 */
1021 1022 1023 1024
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
1025
	struct cgroup *cgrp = &root->top_cgroup;
1026 1027
	int i;

B
Ben Blum 已提交
1028
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1029
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1030

1031 1032 1033 1034
	removed_bits = root->actual_subsys_bits & ~final_bits;
	added_bits = final_bits & ~root->actual_subsys_bits;
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1035
		unsigned long bit = 1UL << i;
1036 1037 1038
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
B
Ben Blum 已提交
1039 1040 1041 1042 1043 1044
		/*
		 * 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);
1045 1046 1047 1048 1049 1050 1051 1052 1053 1054
		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 */
1055
	if (root->number_of_cgroups > 1)
1056 1057 1058 1059 1060 1061 1062 1063
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
		if (bit & added_bits) {
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1064
			BUG_ON(ss == NULL);
1065
			BUG_ON(cgrp->subsys[i]);
1066 1067
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1068 1069
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1070
			list_move(&ss->sibling, &root->subsys_list);
1071
			ss->root = root;
1072
			if (ss->bind)
1073
				ss->bind(cgrp);
B
Ben Blum 已提交
1074
			/* refcount was already taken, and we're keeping it */
1075 1076
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
B
Ben Blum 已提交
1077
			BUG_ON(ss == NULL);
1078 1079
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1080
			if (ss->bind)
1081
				ss->bind(dummytop);
1082
			dummytop->subsys[i]->cgroup = dummytop;
1083
			cgrp->subsys[i] = NULL;
1084
			subsys[i]->root = &rootnode;
1085
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1086 1087
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1088 1089
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1090
			BUG_ON(ss == NULL);
1091
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1092 1093 1094 1095 1096 1097 1098 1099
			/*
			 * 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
1100 1101
		} else {
			/* Subsystem state shouldn't exist */
1102
			BUG_ON(cgrp->subsys[i]);
1103 1104 1105 1106 1107 1108 1109 1110
		}
	}
	root->subsys_bits = root->actual_subsys_bits = final_bits;
	synchronize_rcu();

	return 0;
}

1111
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1112
{
1113
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1114 1115
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1116
	mutex_lock(&cgroup_root_mutex);
1117 1118 1119 1120
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
1121 1122
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1123 1124
	if (clone_children(&root->top_cgroup))
		seq_puts(seq, ",clone_children");
1125 1126
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1127
	mutex_unlock(&cgroup_root_mutex);
1128 1129 1130 1131 1132 1133
	return 0;
}

struct cgroup_sb_opts {
	unsigned long subsys_bits;
	unsigned long flags;
1134
	char *release_agent;
1135
	bool clone_children;
1136
	char *name;
1137 1138
	/* User explicitly requested empty subsystem */
	bool none;
1139 1140

	struct cgroupfs_root *new_root;
1141

1142 1143
};

B
Ben Blum 已提交
1144 1145
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
Ben Blum 已提交
1146 1147 1148
 * 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
1149
 */
B
Ben Blum 已提交
1150
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1151
{
1152 1153
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1154
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1155 1156
	int i;
	bool module_pin_failed = false;
1157

B
Ben Blum 已提交
1158 1159
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1160 1161 1162
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1163

1164
	memset(opts, 0, sizeof(*opts));
1165 1166 1167 1168

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1169
		if (!strcmp(token, "none")) {
1170 1171
			/* Explicitly have no subsystems */
			opts->none = true;
1172 1173 1174 1175 1176 1177 1178 1179 1180 1181
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1182
			set_bit(ROOT_NOPREFIX, &opts->flags);
1183 1184 1185
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1186
			opts->clone_children = true;
1187 1188 1189
			continue;
		}
		if (!strncmp(token, "release_agent=", 14)) {
1190 1191 1192
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1193
			opts->release_agent =
1194
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1195 1196
			if (!opts->release_agent)
				return -ENOMEM;
1197 1198 1199
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
			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,
1217
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1218 1219 1220
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247

			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;
			set_bit(i, &opts->subsys_bits);
			one_ss = true;

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1248 1249
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1250
	 */
1251
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1252 1253 1254 1255 1256 1257 1258
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
			set_bit(i, &opts->subsys_bits);
1259 1260 1261
		}
	}

1262 1263
	/* Consistency checks */

1264 1265 1266 1267 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.
	 */
	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
	    (opts->subsys_bits & mask))
		return -EINVAL;

1273 1274 1275 1276 1277 1278 1279 1280 1281

	/* Can't specify "none" and some subsystems */
	if (opts->subsys_bits && opts->none)
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1282
	if (!opts->subsys_bits && !opts->name)
1283 1284
		return -EINVAL;

B
Ben Blum 已提交
1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317
	/*
	 * 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.
	 */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

		if (!(bit & opts->subsys_bits))
			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.
		 */
		for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

			if (!(bit & opts->subsys_bits))
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1318 1319 1320
	return 0;
}

B
Ben Blum 已提交
1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332
static void drop_parsed_module_refcounts(unsigned long subsys_bits)
{
	int i;
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

		if (!(bit & subsys_bits))
			continue;
		module_put(subsys[i]->module);
	}
}

1333 1334 1335 1336
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1337
	struct cgroup *cgrp = &root->top_cgroup;
1338 1339
	struct cgroup_sb_opts opts;

1340
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1341
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1342
	mutex_lock(&cgroup_root_mutex);
1343 1344 1345 1346 1347 1348

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

1349 1350 1351 1352 1353
	/* See feature-removal-schedule.txt */
	if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

B
Ben Blum 已提交
1354 1355 1356
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1357
		ret = -EINVAL;
B
Ben Blum 已提交
1358
		drop_parsed_module_refcounts(opts.subsys_bits);
1359 1360 1361
		goto out_unlock;
	}

1362
	ret = rebind_subsystems(root, opts.subsys_bits);
B
Ben Blum 已提交
1363 1364
	if (ret) {
		drop_parsed_module_refcounts(opts.subsys_bits);
1365
		goto out_unlock;
B
Ben Blum 已提交
1366
	}
1367

1368 1369
	/* clear out any existing files and repopulate subsystem files */
	cgroup_clear_directory(cgrp->dentry);
1370
	cgroup_populate_dir(cgrp);
1371

1372 1373
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1374
 out_unlock:
1375
	kfree(opts.release_agent);
1376
	kfree(opts.name);
T
Tejun Heo 已提交
1377
	mutex_unlock(&cgroup_root_mutex);
1378
	mutex_unlock(&cgroup_mutex);
1379
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1380 1381 1382
	return ret;
}

1383
static const struct super_operations cgroup_ops = {
1384 1385 1386 1387 1388 1389
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1390 1391 1392 1393
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1394
	INIT_LIST_HEAD(&cgrp->files);
1395 1396
	INIT_LIST_HEAD(&cgrp->css_sets);
	INIT_LIST_HEAD(&cgrp->release_list);
1397 1398
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1399 1400
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
1401
}
1402

1403 1404
static void init_cgroup_root(struct cgroupfs_root *root)
{
1405
	struct cgroup *cgrp = &root->top_cgroup;
1406

1407 1408
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1409
	INIT_LIST_HEAD(&root->allcg_list);
1410
	root->number_of_cgroups = 1;
1411 1412
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1413
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1414
	init_cgroup_housekeeping(cgrp);
1415 1416
}

1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441
static bool init_root_id(struct cgroupfs_root *root)
{
	int ret = 0;

	do {
		if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
			return false;
		spin_lock(&hierarchy_id_lock);
		/* Try to allocate the next unused ID */
		ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
					&root->hierarchy_id);
		if (ret == -ENOSPC)
			/* Try again starting from 0 */
			ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
		if (!ret) {
			next_hierarchy_id = root->hierarchy_id + 1;
		} else if (ret != -EAGAIN) {
			/* Can only get here if the 31-bit IDR is full ... */
			BUG_ON(ret);
		}
		spin_unlock(&hierarchy_id_lock);
	} while (ret);
	return true;
}

1442 1443
static int cgroup_test_super(struct super_block *sb, void *data)
{
1444
	struct cgroup_sb_opts *opts = data;
1445 1446
	struct cgroupfs_root *root = sb->s_fs_info;

1447 1448 1449
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1450

1451 1452 1453 1454 1455 1456
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
	if ((opts->subsys_bits || opts->none)
	    && (opts->subsys_bits != root->subsys_bits))
1457 1458 1459 1460 1461
		return 0;

	return 1;
}

1462 1463 1464 1465
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1466
	if (!opts->subsys_bits && !opts->none)
1467 1468 1469 1470 1471 1472
		return NULL;

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

1473 1474 1475 1476
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1477
	init_cgroup_root(root);
1478

1479 1480 1481 1482 1483 1484
	root->subsys_bits = opts->subsys_bits;
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1485 1486
	if (opts->clone_children)
		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1487 1488 1489
	return root;
}

1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501
static void cgroup_drop_root(struct cgroupfs_root *root)
{
	if (!root)
		return;

	BUG_ON(!root->hierarchy_id);
	spin_lock(&hierarchy_id_lock);
	ida_remove(&hierarchy_ida, root->hierarchy_id);
	spin_unlock(&hierarchy_id_lock);
	kfree(root);
}

1502 1503 1504
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1505 1506 1507 1508 1509 1510
	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;

1511
	BUG_ON(!opts->subsys_bits && !opts->none);
1512 1513 1514 1515 1516

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

1517 1518
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529

	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
1530 1531
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1532
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1533 1534
	};

1535 1536 1537 1538 1539 1540 1541 1542 1543 1544
	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);
1545 1546
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1547
		return -ENOMEM;
A
Al Viro 已提交
1548 1549
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1550 1551 1552
	return 0;
}

A
Al Viro 已提交
1553
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1554
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1555
			 void *data)
1556 1557
{
	struct cgroup_sb_opts opts;
1558
	struct cgroupfs_root *root;
1559 1560
	int ret = 0;
	struct super_block *sb;
1561
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1562
	struct inode *inode;
1563 1564

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1565
	mutex_lock(&cgroup_mutex);
1566
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1567
	mutex_unlock(&cgroup_mutex);
1568 1569
	if (ret)
		goto out_err;
1570

1571 1572 1573 1574 1575 1576 1577
	/*
	 * 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
1578
		goto drop_modules;
1579
	}
1580
	opts.new_root = new_root;
1581

1582
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1583
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1584
	if (IS_ERR(sb)) {
1585
		ret = PTR_ERR(sb);
1586
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1587
		goto drop_modules;
1588 1589
	}

1590 1591 1592 1593 1594
	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 */
		struct list_head tmp_cg_links;
1595
		struct cgroup *root_cgrp = &root->top_cgroup;
1596
		struct cgroupfs_root *existing_root;
1597
		const struct cred *cred;
1598
		int i;
1599 1600 1601 1602 1603 1604

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1605
		inode = sb->s_root->d_inode;
1606

1607
		mutex_lock(&inode->i_mutex);
1608
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1609
		mutex_lock(&cgroup_root_mutex);
1610

T
Tejun Heo 已提交
1611 1612 1613 1614 1615 1616
		/* 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;
1617

1618 1619 1620 1621 1622 1623 1624 1625
		/*
		 * 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
		 */
		ret = allocate_cg_links(css_set_count, &tmp_cg_links);
T
Tejun Heo 已提交
1626 1627
		if (ret)
			goto unlock_drop;
1628

1629 1630
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
1631
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1632
			goto unlock_drop;
1633
		}
B
Ben Blum 已提交
1634 1635 1636 1637 1638
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1639 1640 1641 1642 1643

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

		list_add(&root->root_list, &roots);
1644
		root_count++;
1645

1646
		sb->s_root->d_fsdata = root_cgrp;
1647 1648
		root->top_cgroup.dentry = sb->s_root;

1649 1650 1651
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1652 1653 1654
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1655
			struct css_set *cg;
1656

1657 1658
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1659
		}
1660 1661 1662 1663
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1664 1665
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1666 1667
		BUG_ON(root->number_of_cgroups != 1);

1668
		cred = override_creds(&init_cred);
1669
		cgroup_populate_dir(root_cgrp);
1670
		revert_creds(cred);
T
Tejun Heo 已提交
1671
		mutex_unlock(&cgroup_root_mutex);
1672
		mutex_unlock(&cgroup_mutex);
1673
		mutex_unlock(&inode->i_mutex);
1674 1675 1676 1677 1678
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1679
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1680 1681
		/* no subsys rebinding, so refcounts don't change */
		drop_parsed_module_refcounts(opts.subsys_bits);
1682 1683
	}

1684 1685
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1686
	return dget(sb->s_root);
1687

T
Tejun Heo 已提交
1688 1689 1690 1691
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1692
 drop_new_super:
1693
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1694 1695
 drop_modules:
	drop_parsed_module_refcounts(opts.subsys_bits);
1696 1697 1698
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1699
	return ERR_PTR(ret);
1700 1701 1702 1703
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1704
	struct cgroup *cgrp = &root->top_cgroup;
1705
	int ret;
K
KOSAKI Motohiro 已提交
1706 1707
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1708 1709 1710 1711

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1712 1713
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1714 1715

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1716
	mutex_lock(&cgroup_root_mutex);
1717 1718 1719 1720 1721 1722

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

1723 1724 1725 1726 1727
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1728 1729 1730

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1731
		list_del(&link->cg_link_list);
1732
		list_del(&link->cgrp_link_list);
1733 1734 1735 1736
		kfree(link);
	}
	write_unlock(&css_set_lock);

1737 1738 1739 1740
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1741

T
Tejun Heo 已提交
1742
	mutex_unlock(&cgroup_root_mutex);
1743 1744 1745
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1746
	cgroup_drop_root(root);
1747 1748 1749 1750
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1751
	.mount = cgroup_mount,
1752 1753 1754
	.kill_sb = cgroup_kill_sb,
};

1755 1756
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1757 1758 1759 1760 1761 1762
/**
 * 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
 *
1763 1764 1765
 * Called with cgroup_mutex held or else with an RCU-protected cgroup
 * reference.  Writes path of cgroup into buf.  Returns 0 on success,
 * -errno on error.
1766
 */
1767
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1768 1769
{
	char *start;
1770 1771
	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
						      cgroup_lock_is_held());
1772

1773
	if (!dentry || cgrp == dummytop) {
1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1786
		int len = dentry->d_name.len;
1787

1788 1789
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1790
		memcpy(start, dentry->d_name.name, len);
1791 1792
		cgrp = cgrp->parent;
		if (!cgrp)
1793
			break;
1794 1795 1796

		dentry = rcu_dereference_check(cgrp->dentry,
					       cgroup_lock_is_held());
1797
		if (!cgrp->parent)
1798 1799 1800 1801 1802 1803 1804 1805
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1806
EXPORT_SYMBOL_GPL(cgroup_path);
1807

1808 1809 1810
/*
 * Control Group taskset
 */
1811 1812 1813
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1814
	struct css_set		*cg;
1815 1816
};

1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 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 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887
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
1888 1889 1890 1891 1892
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
 * 'guarantee' is set if the caller promises that a new css_set for the task
 * will already exist. If not set, this function might sleep, and can fail with
1893
 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1894
 */
1895 1896
static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
				struct task_struct *tsk, struct css_set *newcg)
B
Ben Blum 已提交
1897 1898 1899 1900
{
	struct css_set *oldcg;

	/*
1901 1902 1903
	 * 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
1904
	 */
1905
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927
	oldcg = tsk->cgroups;

	task_lock(tsk);
	rcu_assign_pointer(tsk->cgroups, newcg);
	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))
		list_move(&tsk->cg_list, &newcg->tasks);
	write_unlock(&css_set_lock);

	/*
	 * We just gained a reference on oldcg by taking it from the task. As
	 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
	 * it here; it will be freed under RCU.
	 */
	put_css_set(oldcg);

	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
}

L
Li Zefan 已提交
1928 1929 1930 1931
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1932
 *
1933 1934
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1935
 */
1936
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1937
{
1938
	int retval = 0;
1939
	struct cgroup_subsys *ss, *failed_ss = NULL;
1940 1941
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1942
	struct cgroup_taskset tset = { };
1943
	struct css_set *newcg;
1944

1945 1946 1947
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1948 1949

	/* Nothing to do if the task is already in that cgroup */
1950
	oldcgrp = task_cgroup_from_root(tsk, root);
1951
	if (cgrp == oldcgrp)
1952 1953
		return 0;

1954 1955 1956
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1957 1958
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1959
			retval = ss->can_attach(cgrp, &tset);
1960 1961 1962 1963 1964 1965 1966 1967 1968 1969
			if (retval) {
				/*
				 * Remember on which subsystem the can_attach()
				 * failed, so that we only call cancel_attach()
				 * against the subsystems whose can_attach()
				 * succeeded. (See below)
				 */
				failed_ss = ss;
				goto out;
			}
1970 1971 1972
		}
	}

1973 1974 1975
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
1976
		goto out;
1977 1978 1979
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1980

1981
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1982
		if (ss->attach)
1983
			ss->attach(cgrp, &tset);
1984
	}
B
Ben Blum 已提交
1985

1986
	synchronize_rcu();
1987 1988 1989 1990 1991

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1992
	cgroup_wakeup_rmdir_waiter(cgrp);
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
out:
	if (retval) {
		for_each_subsys(root, ss) {
			if (ss == failed_ss)
				/*
				 * This subsystem was the one that failed the
				 * can_attach() check earlier, so we don't need
				 * to call cancel_attach() against it or any
				 * remaining subsystems.
				 */
				break;
			if (ss->cancel_attach)
2005
				ss->cancel_attach(cgrp, &tset);
2006 2007 2008
		}
	}
	return retval;
2009 2010
}

2011
/**
M
Michael S. Tsirkin 已提交
2012 2013
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
2014 2015
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
2016
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2017 2018 2019 2020 2021 2022
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
2023 2024 2025
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
2026 2027 2028 2029 2030 2031 2032
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
2033
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2034

B
Ben Blum 已提交
2035 2036 2037 2038 2039
/**
 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
 * @cgrp: the cgroup to attach to
 * @leader: the threadgroup leader task_struct of the group to be attached
 *
2040 2041
 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
 * task_lock of each thread in leader's threadgroup individually in turn.
B
Ben Blum 已提交
2042
 */
2043
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
2044 2045 2046 2047 2048 2049 2050
{
	int retval, i, group_size;
	struct cgroup_subsys *ss, *failed_ss = NULL;
	/* guaranteed to be initialized later, but the compiler needs this */
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
	struct task_struct *tsk;
2051
	struct task_and_cgroup *tc;
2052
	struct flex_array *group;
2053
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2054 2055 2056 2057 2058

	/*
	 * 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
2059 2060
	 * 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
2061 2062
	 */
	group_size = get_nr_threads(leader);
2063
	/* flex_array supports very large thread-groups better than kmalloc. */
2064
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2065 2066
	if (!group)
		return -ENOMEM;
2067 2068 2069 2070
	/* pre-allocate to guarantee space while iterating in rcu read-side. */
	retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
	if (retval)
		goto out_free_group_list;
B
Ben Blum 已提交
2071 2072 2073

	tsk = leader;
	i = 0;
2074 2075 2076 2077 2078 2079
	/*
	 * 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
2080
	do {
2081 2082
		struct task_and_cgroup ent;

2083 2084 2085 2086
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2087 2088
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2089 2090
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2091 2092 2093
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2094 2095 2096 2097
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2098
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2099
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2100 2101
		i++;
	} while_each_thread(leader, tsk);
2102
	rcu_read_unlock();
B
Ben Blum 已提交
2103 2104
	/* remember the number of threads in the array for later. */
	group_size = i;
2105 2106
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2107

2108 2109
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2110
	if (!group_size)
2111
		goto out_free_group_list;
2112

B
Ben Blum 已提交
2113 2114 2115 2116 2117
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2118
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130
			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++) {
2131
		tc = flex_array_get(group, i);
2132 2133 2134 2135
		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
2136 2137 2138 2139
		}
	}

	/*
2140 2141 2142
	 * 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
2143 2144
	 */
	for (i = 0; i < group_size; i++) {
2145
		tc = flex_array_get(group, i);
2146
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2147 2148 2149 2150
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2151
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2152 2153 2154
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2155
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2156 2157 2158 2159 2160 2161 2162 2163
	}

	/*
	 * step 5: success! and cleanup
	 */
	synchronize_rcu();
	cgroup_wakeup_rmdir_waiter(cgrp);
	retval = 0;
2164 2165 2166 2167 2168 2169 2170 2171
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
2172 2173 2174 2175
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2176
			if (ss == failed_ss)
B
Ben Blum 已提交
2177 2178
				break;
			if (ss->cancel_attach)
2179
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2180 2181 2182
		}
	}
out_free_group_list:
2183
	flex_array_free(group);
B
Ben Blum 已提交
2184 2185 2186 2187 2188
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2189 2190
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2191
 */
B
Ben Blum 已提交
2192
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2193 2194
{
	struct task_struct *tsk;
2195
	const struct cred *cred = current_cred(), *tcred;
2196 2197
	int ret;

B
Ben Blum 已提交
2198 2199 2200
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2201 2202
retry_find_task:
	rcu_read_lock();
2203
	if (pid) {
2204
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2205 2206
		if (!tsk) {
			rcu_read_unlock();
2207 2208
			ret= -ESRCH;
			goto out_unlock_cgroup;
2209
		}
B
Ben Blum 已提交
2210 2211 2212 2213
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2214
		tcred = __task_cred(tsk);
2215 2216 2217
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2218
			rcu_read_unlock();
2219 2220
			ret = -EACCES;
			goto out_unlock_cgroup;
2221
		}
2222 2223
	} else
		tsk = current;
2224 2225

	if (threadgroup)
2226
		tsk = tsk->group_leader;
2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238

	/*
	 * Workqueue threads may acquire PF_THREAD_BOUND and become
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
	if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255
	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;
		}
B
Ben Blum 已提交
2256
		ret = cgroup_attach_proc(cgrp, tsk);
2257
	} else
B
Ben Blum 已提交
2258
		ret = cgroup_attach_task(cgrp, tsk);
2259 2260
	threadgroup_unlock(tsk);

2261
	put_task_struct(tsk);
2262
out_unlock_cgroup:
B
Ben Blum 已提交
2263
	cgroup_unlock();
2264 2265 2266
	return ret;
}

2267
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2268 2269 2270 2271 2272
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2273
{
2274
	return attach_task_by_pid(cgrp, tgid, true);
2275 2276
}

2277 2278 2279 2280
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2281 2282
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2283
 */
2284
bool cgroup_lock_live_group(struct cgroup *cgrp)
2285 2286 2287 2288 2289 2290 2291 2292
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2293
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2294 2295 2296 2297 2298

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);
2299 2300
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2301 2302
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2303
	mutex_lock(&cgroup_root_mutex);
2304
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2305
	mutex_unlock(&cgroup_root_mutex);
2306
	cgroup_unlock();
2307 2308 2309 2310 2311 2312 2313 2314 2315 2316
	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');
2317
	cgroup_unlock();
2318 2319 2320
	return 0;
}

2321 2322 2323
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2324
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2325 2326 2327
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2328
{
2329
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340
	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 */
2341
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2342
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2343 2344 2345 2346
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2347
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2348 2349 2350 2351
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2352 2353 2354 2355 2356
	if (!retval)
		retval = nbytes;
	return retval;
}

2357 2358 2359 2360 2361
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)
{
2362
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376
	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
2377 2378 2379 2380
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2381 2382

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2383
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2384 2385
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2386
out:
2387 2388 2389 2390 2391
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2392 2393 2394 2395
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);
2396
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2397

2398
	if (cgroup_is_removed(cgrp))
2399
		return -ENODEV;
2400
	if (cft->write)
2401
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2402 2403
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2404 2405
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2406 2407 2408 2409
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2410
	return -EINVAL;
2411 2412
}

2413 2414 2415 2416
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2417
{
2418
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2419
	u64 val = cft->read_u64(cgrp, cft);
2420 2421 2422 2423 2424
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2425 2426 2427 2428 2429
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2430
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2431 2432 2433 2434 2435 2436
	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);
}

2437 2438 2439 2440
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);
2441
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2442

2443
	if (cgroup_is_removed(cgrp))
2444 2445 2446
		return -ENODEV;

	if (cft->read)
2447
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2448 2449
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2450 2451
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2452 2453 2454
	return -EINVAL;
}

2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474
/*
 * 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;
2475 2476 2477 2478 2479 2480 2481 2482
	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);
2483 2484
}

2485
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2486 2487 2488 2489 2490 2491
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2492
static const struct file_operations cgroup_seqfile_operations = {
2493
	.read = seq_read,
2494
	.write = cgroup_file_write,
2495 2496 2497 2498
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2499 2500 2501 2502 2503 2504 2505 2506 2507
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);
2508

2509
	if (cft->read_map || cft->read_seq_string) {
2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520
		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)
2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550
		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)
{
	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;
	return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
}

2551
static const struct file_operations cgroup_file_operations = {
2552 2553 2554 2555 2556 2557 2558
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

2559
static const struct inode_operations cgroup_dir_inode_operations = {
2560
	.lookup = cgroup_lookup,
2561 2562 2563 2564 2565
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

A
Al Viro 已提交
2566
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2567 2568 2569 2570 2571 2572 2573
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2574 2575 2576 2577 2578 2579 2580 2581 2582 2583
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
	if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2584
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2585 2586
				struct super_block *sb)
{
2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606
	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);

		/* start with the directory inode held, so that we can
		 * populate it without racing with another mkdir */
2607
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2608 2609 2610 2611 2612 2613 2614 2615 2616 2617
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2618 2619 2620 2621 2622
 * cgroup_create_dir - create a directory for an object.
 * @cgrp: the cgroup we create the directory for. It must have a valid
 *        ->parent field. And we are going to fill its ->dentry field.
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new directory.
2623
 */
2624
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
A
Al Viro 已提交
2625
				umode_t mode)
2626 2627 2628 2629
{
	struct dentry *parent;
	int error = 0;

2630 2631
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2632
	if (!error) {
2633
		dentry->d_fsdata = cgrp;
2634
		inc_nlink(parent->d_inode);
2635
		rcu_assign_pointer(cgrp->dentry, dentry);
2636 2637 2638 2639 2640 2641 2642
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2643 2644 2645 2646 2647 2648 2649 2650 2651
/**
 * 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
2652
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2653
{
A
Al Viro 已提交
2654
	umode_t mode = 0;
L
Li Zefan 已提交
2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669

	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
2670 2671
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			   const struct cftype *cft)
2672
{
2673
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2674
	struct cgroup *parent = __d_cgrp(dir);
2675
	struct dentry *dentry;
T
Tejun Heo 已提交
2676
	struct cfent *cfe;
2677
	int error;
A
Al Viro 已提交
2678
	umode_t mode;
2679
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2680 2681 2682 2683 2684 2685 2686

	/* does @cft->flags tell us to skip creation on @cgrp? */
	if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
		return 0;
	if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
		return 0;

2687
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2688 2689 2690 2691
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2692

2693
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2694 2695 2696 2697 2698

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

2699
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2700
	if (IS_ERR(dentry)) {
2701
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716
		goto out;
	}

	mode = cgroup_file_mode(cft);
	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
	if (!error) {
		cfe->type = (void *)cft;
		cfe->dentry = dentry;
		dentry->d_fsdata = cfe;
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
	}
	dput(dentry);
out:
	kfree(cfe);
2717 2718 2719
	return error;
}

2720 2721
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      const struct cftype cfts[], bool is_add)
2722
{
T
Tejun Heo 已提交
2723 2724 2725 2726
	const struct cftype *cft;
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2727 2728 2729 2730
		if (is_add)
			err = cgroup_add_file(cgrp, subsys, cft);
		else
			err = cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2731
		if (err) {
2732 2733
			pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
				   is_add ? "add" : "remove", cft->name, err);
T
Tejun Heo 已提交
2734 2735
			ret = err;
		}
2736
	}
T
Tejun Heo 已提交
2737
	return ret;
2738 2739
}

2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756
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,
2757
			       const struct cftype *cfts, bool is_add)
2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782
	__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))
2783
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818
		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.
 */
int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
{
	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);
2819
	cgroup_cfts_commit(ss, cfts, true);
2820 2821 2822 2823 2824

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855
/**
 * 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.
 */
int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
{
	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
2856 2857 2858 2859 2860 2861
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2862
int cgroup_task_count(const struct cgroup *cgrp)
2863 2864
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2865
	struct cg_cgroup_link *link;
2866 2867

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2868
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2869
		count += atomic_read(&link->cg->refcount);
2870 2871
	}
	read_unlock(&css_set_lock);
2872 2873 2874
	return count;
}

2875 2876 2877 2878
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2879
static void cgroup_advance_iter(struct cgroup *cgrp,
2880
				struct cgroup_iter *it)
2881 2882 2883 2884 2885 2886 2887 2888
{
	struct list_head *l = it->cg_link;
	struct cg_cgroup_link *link;
	struct css_set *cg;

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2889
		if (l == &cgrp->css_sets) {
2890 2891 2892
			it->cg_link = NULL;
			return;
		}
2893
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2894 2895 2896 2897 2898 2899
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2900 2901 2902 2903 2904 2905
/*
 * 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().
 */
2906
static void cgroup_enable_task_cg_lists(void)
2907 2908 2909 2910
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2911 2912 2913 2914 2915 2916 2917 2918
	/*
	 * 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);
2919 2920
	do_each_thread(g, p) {
		task_lock(p);
2921 2922 2923 2924 2925 2926
		/*
		 * 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))
2927 2928 2929
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2930
	read_unlock(&tasklist_lock);
2931 2932 2933
	write_unlock(&css_set_lock);
}

2934
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2935
	__acquires(css_set_lock)
2936 2937 2938 2939 2940 2941
{
	/*
	 * 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.
	 */
2942 2943 2944
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2945
	read_lock(&css_set_lock);
2946 2947
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2948 2949
}

2950
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2951 2952 2953 2954
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2955
	struct cg_cgroup_link *link;
2956 2957 2958 2959 2960 2961 2962

	/* If the iterator cg is NULL, we have no tasks */
	if (!it->cg_link)
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
	/* Advance iterator to find next entry */
	l = l->next;
2963 2964
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2965 2966
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2967
		cgroup_advance_iter(cgrp, it);
2968 2969 2970 2971 2972 2973
	} else {
		it->task = l;
	}
	return res;
}

2974
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2975
	__releases(css_set_lock)
2976 2977 2978 2979
{
	read_unlock(&css_set_lock);
}

2980 2981 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 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116
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++) {
3117
			struct task_struct *q = heap->ptrs[i];
3118
			if (i == 0) {
3119 3120
				latest_time = q->start_time;
				latest_task = q;
3121 3122
			}
			/* Process the task per the caller's callback */
3123 3124
			scan->process_task(q, scan);
			put_task_struct(q);
3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139
		}
		/*
		 * 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;
}

3140
/*
3141
 * Stuff for reading the 'tasks'/'procs' files.
3142 3143 3144 3145 3146 3147 3148 3149
 *
 * 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.
 *
 */

3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181
/* 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;
};

3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217
/*
 * 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);
}
static void *pidlist_resize(void *p, int newcount)
{
	void *newlist;
	/* note: if new alloc fails, old p will still be valid either way */
	if (is_vmalloc_addr(p)) {
		newlist = vmalloc(newcount * sizeof(pid_t));
		if (!newlist)
			return NULL;
		memcpy(newlist, p, newcount * sizeof(pid_t));
		vfree(p);
	} else {
		newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
	}
	return newlist;
}

3218
/*
3219 3220 3221 3222
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
 * If the new stripped list is sufficiently smaller and there's enough memory
 * to allocate a new buffer, will let go of the unneeded memory. Returns the
 * number of unique elements.
3223
 */
3224 3225 3226
/* is the size difference enough that we should re-allocate the array? */
#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
static int pidlist_uniq(pid_t **p, int length)
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
	int src, dest = 1;
	pid_t *list = *p;
	pid_t *newlist;

	/*
	 * 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:
	/*
	 * if the length difference is large enough, we want to allocate a
	 * smaller buffer to save memory. if this fails due to out of memory,
	 * we'll just stay with what we've got.
	 */
	if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3257
		newlist = pidlist_resize(list, dest);
3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279
/*
 * 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 */
3280 3281
	struct pid_namespace *ns = current->nsproxy->pid_ns;

3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305
	/*
	 * 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;
3306
	l->key.ns = get_pid_ns(ns);
3307 3308 3309 3310 3311 3312 3313 3314
	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;
}

3315 3316 3317
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3318 3319
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3320 3321 3322 3323
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3324 3325
	struct cgroup_iter it;
	struct task_struct *tsk;
3326 3327 3328 3329 3330 3331 3332 3333 3334
	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);
3335
	array = pidlist_allocate(length);
3336 3337 3338
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3339 3340
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3341
		if (unlikely(n == length))
3342
			break;
3343
		/* get tgid or pid for procs or tasks file respectively */
3344 3345 3346 3347
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3348 3349
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3350
	}
3351
	cgroup_iter_end(cgrp, &it);
3352 3353 3354
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3355
	if (type == CGROUP_FILE_PROCS)
3356
		length = pidlist_uniq(&array, length);
3357 3358
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3359
		pidlist_free(array);
3360
		return -ENOMEM;
3361
	}
3362
	/* store array, freeing old if necessary - lock already held */
3363
	pidlist_free(l->list);
3364 3365 3366 3367
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3368
	*lp = l;
3369
	return 0;
3370 3371
}

B
Balbir Singh 已提交
3372
/**
L
Li Zefan 已提交
3373
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3374 3375 3376
 * @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
3377 3378 3379
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3380 3381 3382 3383
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3384
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3385 3386
	struct cgroup_iter it;
	struct task_struct *tsk;
3387

B
Balbir Singh 已提交
3388
	/*
3389 3390
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3391
	 */
3392 3393
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3394 3395 3396
		 goto err;

	ret = 0;
3397
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3398

3399 3400
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419
		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;
		}
	}
3420
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3421 3422 3423 3424 3425

err:
	return ret;
}

3426

3427
/*
3428
 * seq_file methods for the tasks/procs files. The seq_file position is the
3429
 * next pid to display; the seq_file iterator is a pointer to the pid
3430
 * in the cgroup->l->list array.
3431
 */
3432

3433
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3434
{
3435 3436 3437 3438 3439 3440
	/*
	 * 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
	 */
3441
	struct cgroup_pidlist *l = s->private;
3442 3443 3444
	int index = 0, pid = *pos;
	int *iter;

3445
	down_read(&l->mutex);
3446
	if (pid) {
3447
		int end = l->length;
S
Stephen Rothwell 已提交
3448

3449 3450
		while (index < end) {
			int mid = (index + end) / 2;
3451
			if (l->list[mid] == pid) {
3452 3453
				index = mid;
				break;
3454
			} else if (l->list[mid] <= pid)
3455 3456 3457 3458 3459 3460
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3461
	if (index >= l->length)
3462 3463
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3464
	iter = l->list + index;
3465 3466 3467 3468
	*pos = *iter;
	return iter;
}

3469
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3470
{
3471 3472
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3473 3474
}

3475
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3476
{
3477 3478 3479
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492
	/*
	 * 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;
	}
}

3493
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3494 3495 3496
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3497

3498 3499 3500 3501 3502 3503 3504 3505 3506
/*
 * 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,
3507 3508
};

3509
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3510
{
3511 3512 3513 3514 3515 3516 3517
	/*
	 * 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);
3518 3519 3520
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3521 3522 3523
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3524
		pidlist_free(l->list);
3525 3526 3527 3528
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3529
	}
3530
	mutex_unlock(&l->owner->pidlist_mutex);
3531
	up_write(&l->mutex);
3532 3533
}

3534
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3535
{
3536
	struct cgroup_pidlist *l;
3537 3538
	if (!(file->f_mode & FMODE_READ))
		return 0;
3539 3540 3541 3542 3543 3544
	/*
	 * 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);
3545 3546 3547
	return seq_release(inode, file);
}

3548
static const struct file_operations cgroup_pidlist_operations = {
3549 3550 3551
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3552
	.release = cgroup_pidlist_release,
3553 3554
};

3555
/*
3556 3557 3558
 * 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.
3559
 */
3560
/* helper function for the two below it */
3561
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3562
{
3563
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3564
	struct cgroup_pidlist *l;
3565
	int retval;
3566

3567
	/* Nothing to do for write-only files */
3568 3569 3570
	if (!(file->f_mode & FMODE_READ))
		return 0;

3571
	/* have the array populated */
3572
	retval = pidlist_array_load(cgrp, type, &l);
3573 3574 3575 3576
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3577

3578
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3579
	if (retval) {
3580
		cgroup_release_pid_array(l);
3581
		return retval;
3582
	}
3583
	((struct seq_file *)file->private_data)->private = l;
3584 3585
	return 0;
}
3586 3587
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3588
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3589 3590 3591
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3592
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3593
}
3594

3595
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3596 3597
					    struct cftype *cft)
{
3598
	return notify_on_release(cgrp);
3599 3600
}

3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612
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;
}

3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627
/*
 * 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;

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

	eventfd_ctx_put(event->eventfd);
	kfree(event);
3628
	dput(cgrp->dentry);
3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644
}

/*
 * 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) {
C
Changli Gao 已提交
3645
		__remove_wait_queue(event->wqh, &event->wait);
3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722
		spin_lock(&cgrp->event_list_lock);
		list_del(&event->list);
		spin_unlock(&cgrp->event_list_lock);
		/*
		 * We are in atomic context, but cgroup_event_remove() may
		 * sleep, so we have to call it in workqueue.
		 */
		schedule_work(&event->remove);
	}

	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;
	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
3723 3724
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749
	if (ret < 0)
		goto fail;

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

	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;

	if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
		event->cft->unregister_event(cgrp, event->cft, event->eventfd);
		ret = 0;
		goto fail;
	}

3750 3751 3752 3753 3754 3755 3756
	/*
	 * 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);

3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780
	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;
}

3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
	return clone_children(cgrp);
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
	else
		clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
	return 0;
}

3798 3799 3800
/*
 * for the common functions, 'private' gives the type of file
 */
3801 3802
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3803 3804 3805 3806
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3807
		.write_u64 = cgroup_tasks_write,
3808
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3809
		.mode = S_IRUGO | S_IWUSR,
3810
	},
3811 3812 3813
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3814
		.write_u64 = cgroup_procs_write,
3815
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3816
		.mode = S_IRUGO | S_IWUSR,
3817
	},
3818 3819
	{
		.name = "notify_on_release",
3820
		.read_u64 = cgroup_read_notify_on_release,
3821
		.write_u64 = cgroup_write_notify_on_release,
3822
	},
3823 3824 3825 3826 3827
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3828 3829 3830 3831 3832
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3833 3834 3835 3836 3837 3838 3839
	{
		.name = "release_agent",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.read_seq_string = cgroup_release_agent_show,
		.write_string = cgroup_release_agent_write,
		.max_write_len = PATH_MAX,
	},
T
Tejun Heo 已提交
3840
	{ }	/* terminate */
3841 3842
};

3843
static int cgroup_populate_dir(struct cgroup *cgrp)
3844 3845 3846 3847
{
	int err;
	struct cgroup_subsys *ss;

3848
	err = cgroup_addrm_files(cgrp, NULL, files, true);
3849 3850 3851
	if (err < 0)
		return err;

3852
	/* process cftsets of each subsystem */
3853
	for_each_subsys(cgrp->root, ss) {
3854 3855
		struct cftype_set *set;

T
Tejun Heo 已提交
3856
		list_for_each_entry(set, &ss->cftsets, node)
3857
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
3858
	}
3859

K
KAMEZAWA Hiroyuki 已提交
3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870
	/* 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);
	}
3871 3872 3873 3874

	return 0;
}

3875 3876 3877 3878
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
3879 3880
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
3881

3882 3883 3884
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
3885 3886
}

3887 3888
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
3889
			       struct cgroup *cgrp)
3890
{
3891
	css->cgroup = cgrp;
P
Paul Menage 已提交
3892
	atomic_set(&css->refcnt, 1);
3893
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
3894
	css->id = NULL;
3895
	if (cgrp == dummytop)
3896
		set_bit(CSS_ROOT, &css->flags);
3897 3898
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
3899 3900

	/*
3901 3902 3903 3904
	 * 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().
3905 3906
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
3907 3908 3909
}

/*
L
Li Zefan 已提交
3910 3911 3912 3913
 * 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
3914
 *
L
Li Zefan 已提交
3915
 * Must be called with the mutex on the parent inode held
3916 3917
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
3918
			     umode_t mode)
3919
{
3920
	struct cgroup *cgrp;
3921 3922 3923 3924 3925
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

3926 3927
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
3928 3929
		return -ENOMEM;

3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941
	/*
	 * 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;
		goto err_free;
	}

3942 3943 3944 3945 3946 3947 3948
	/* 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);

3949
	init_cgroup_housekeeping(cgrp);
3950

3951 3952 3953
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
3954

3955 3956 3957
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

3958 3959 3960
	if (clone_children(parent))
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);

3961
	for_each_subsys(root, ss) {
3962
		struct cgroup_subsys_state *css = ss->create(cgrp);
3963

3964 3965 3966 3967
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
3968
		init_cgroup_css(css, ss, cgrp);
3969 3970 3971
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
3972
				goto err_destroy;
3973
		}
K
KAMEZAWA Hiroyuki 已提交
3974
		/* At error, ->destroy() callback has to free assigned ID. */
3975
		if (clone_children(parent) && ss->post_clone)
3976
			ss->post_clone(cgrp);
3977 3978
	}

3979
	list_add(&cgrp->sibling, &cgrp->parent->children);
3980 3981
	root->number_of_cgroups++;

3982
	err = cgroup_create_dir(cgrp, dentry, mode);
3983 3984 3985
	if (err < 0)
		goto err_remove;

3986
	/* each css holds a ref to the cgroup's dentry */
3987
	for_each_subsys(root, ss)
3988
		dget(dentry);
3989

3990
	/* The cgroup directory was pre-locked for us */
3991
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3992

3993 3994
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);

3995
	err = cgroup_populate_dir(cgrp);
3996 3997 3998
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
3999
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4000 4001 4002 4003 4004

	return 0;

 err_remove:

4005
	list_del(&cgrp->sibling);
4006 4007 4008 4009 4010
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
4011
		if (cgrp->subsys[ss->subsys_id])
4012
			ss->destroy(cgrp);
4013 4014 4015 4016 4017 4018
	}

	mutex_unlock(&cgroup_mutex);

	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
4019
err_free:
4020
	kfree(cgrp);
4021 4022 4023
	return err;
}

4024
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4025 4026 4027 4028 4029 4030 4031
{
	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);
}

4032 4033 4034 4035 4036 4037 4038 4039 4040
/*
 * Check the reference count on each subsystem. Since we already
 * established that there are no tasks in the cgroup, if the css refcount
 * is also 1, then there should be no outstanding references, so the
 * subsystem is safe to destroy. We scan across all subsystems rather than
 * using the per-hierarchy linked list of mounted subsystems since we can
 * be called via check_for_release() with no synchronization other than
 * RCU, and the subsystem linked list isn't RCU-safe.
 */
4041
static int cgroup_has_css_refs(struct cgroup *cgrp)
4042 4043
{
	int i;
4044

B
Ben Blum 已提交
4045 4046 4047 4048 4049
	/*
	 * We won't need to lock the subsys array, because the subsystems
	 * we're concerned about aren't going anywhere since our cgroup root
	 * has a reference on them.
	 */
4050 4051 4052
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
4053

B
Ben Blum 已提交
4054 4055
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
4056
			continue;
4057

4058
		css = cgrp->subsys[ss->subsys_id];
4059 4060
		/*
		 * When called from check_for_release() it's possible
4061 4062 4063 4064
		 * that by this point the cgroup has been removed
		 * and the css deleted. But a false-positive doesn't
		 * matter, since it can only happen if the cgroup
		 * has been deleted and hence no longer needs the
4065 4066 4067
		 * release agent to be called anyway.
		 */
		if (css && css_refcnt(css) > 1)
4068 4069 4070 4071 4072
			return 1;
	}
	return 0;
}

4073 4074
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
4075
	struct cgroup *cgrp = dentry->d_fsdata;
4076 4077
	struct dentry *d;
	struct cgroup *parent;
4078
	DEFINE_WAIT(wait);
4079
	struct cgroup_event *event, *tmp;
4080
	struct cgroup_subsys *ss;
4081
	int ret;
4082 4083 4084

	/* the vfs holds both inode->i_mutex already */
	mutex_lock(&cgroup_mutex);
4085
	if (atomic_read(&cgrp->count) != 0) {
4086 4087 4088
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4089
	if (!list_empty(&cgrp->children)) {
4090 4091 4092
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4093
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
4094

4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105
	/*
	 * In general, subsystem has no css->refcnt after pre_destroy(). But
	 * in racy cases, subsystem may have to get css->refcnt after
	 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
	 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
	 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
	 * and subsystem's reference count handling. Please see css_get/put
	 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
	 */
	set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);

4106
	/*
L
Li Zefan 已提交
4107 4108
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
4109
	 */
4110
	ret = cgroup_call_pre_destroy(cgrp);
4111 4112
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4113
		return ret;
4114
	}
4115

4116 4117
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
4118
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4119
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4120 4121 4122
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4123
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139

	/* block new css_tryget() by deactivating refcnt */
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
	}

	/*
	 * 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
4140 4141
	for_each_subsys(cgrp->root, ss)
		css_put(cgrp->subsys[ss->subsys_id]);
4142

4143 4144
	finish_wait(&cgroup_rmdir_waitq, &wait);
	clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4145

4146
	raw_spin_lock(&release_list_lock);
4147 4148
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
4149
		list_del_init(&cgrp->release_list);
4150
	raw_spin_unlock(&release_list_lock);
4151 4152

	/* delete this cgroup from parent->children */
4153
	list_del_init(&cgrp->sibling);
4154

4155 4156
	list_del_init(&cgrp->allcg_node);

4157
	d = dget(cgrp->dentry);
4158 4159 4160 4161

	cgroup_d_remove_dir(d);
	dput(d);

4162
	set_bit(CGRP_RELEASABLE, &parent->flags);
4163 4164
	check_for_release(parent);

4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
	 * directory to avoid race between userspace and kernelspace
	 */
	spin_lock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
		list_del(&event->list);
		remove_wait_queue(event->wqh, &event->wait);
		eventfd_signal(event->eventfd, 1);
		schedule_work(&event->remove);
	}
	spin_unlock(&cgrp->event_list_lock);

4179 4180 4181 4182
	mutex_unlock(&cgroup_mutex);
	return 0;
}

4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196
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);
	}
}

4197
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4198 4199
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4200 4201

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4202

4203 4204 4205
	/* init base cftset */
	cgroup_init_cftsets(ss);

4206
	/* Create the top cgroup state for this subsystem */
4207
	list_add(&ss->sibling, &rootnode.subsys_list);
4208
	ss->root = &rootnode;
4209
	css = ss->create(dummytop);
4210 4211 4212 4213
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4214
	/* Update the init_css_set to contain a subsys
4215
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4216 4217 4218
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
	init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4219 4220 4221

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

L
Li Zefan 已提交
4222 4223 4224 4225 4226
	/* 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));

4227
	ss->active = 1;
4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238

	/* 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
4239
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272
 * 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)
{
	int i;
	struct cgroup_subsys_state *css;

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
	    ss->create == NULL || ss->destroy == NULL)
		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) {
		/* a few sanity checks */
		BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4273 4274 4275
	/* init base cftset */
	cgroup_init_cftsets(ss);

4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298
	/*
	 * need to register a subsys id before anything else - for example,
	 * init_cgroup_css needs it.
	 */
	mutex_lock(&cgroup_mutex);
	/* find the first empty slot in the array */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		if (subsys[i] == NULL)
			break;
	}
	if (i == CGROUP_SUBSYS_COUNT) {
		/* maximum number of subsystems already registered! */
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
	/* assign ourselves the subsys_id */
	ss->subsys_id = i;
	subsys[i] = ss;

	/*
	 * no ss->create seems to need anything important in the ss struct, so
	 * this can happen first (i.e. before the rootnode attachment).
	 */
4299
	css = ss->create(dummytop);
4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
		subsys[i] = NULL;
		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) {
		int ret = cgroup_init_idr(ss, css);
		if (ret) {
			dummytop->subsys[ss->subsys_id] = NULL;
4317
			ss->destroy(dummytop);
4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357
			subsys[i] = NULL;
			mutex_unlock(&cgroup_mutex);
			return ret;
		}
	}

	/*
	 * 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);
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
		struct css_set *cg;
		struct hlist_node *node, *tmp;
		struct hlist_head *bucket = &css_set_table[i], *new_bucket;

		hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
			/* skip entries that we already rehashed */
			if (cg->subsys[ss->subsys_id])
				continue;
			/* remove existing entry */
			hlist_del(&cg->hlist);
			/* set new value */
			cg->subsys[ss->subsys_id] = css;
			/* recompute hash and restore entry */
			new_bucket = css_set_hash(cg->subsys);
			hlist_add_head(&cg->hlist, new_bucket);
		}
	}
	write_unlock(&css_set_lock);

	ss->active = 1;

	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4358
}
4359
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4360

B
Ben Blum 已提交
4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388
/**
 * 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)
{
	struct cg_cgroup_link *link;
	struct hlist_head *hhead;

	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);
	/* deassign the subsys_id */
	BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4389
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412

	/*
	 * 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);
	list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
		struct css_set *cg = link->cg;

		hlist_del(&cg->hlist);
		BUG_ON(!cg->subsys[ss->subsys_id]);
		cg->subsys[ss->subsys_id] = NULL;
		hhead = css_set_hash(cg->subsys);
		hlist_add_head(&cg->hlist, hhead);
	}
	write_unlock(&css_set_lock);

	/*
	 * remove subsystem's css from the dummytop and free it - need to free
	 * before marking as null because ss->destroy needs the cgrp->subsys
	 * pointer to find their state. note that this also takes care of
	 * freeing the css_id.
	 */
4413
	ss->destroy(dummytop);
B
Ben Blum 已提交
4414 4415 4416 4417 4418 4419
	dummytop->subsys[ss->subsys_id] = NULL;

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

4420
/**
L
Li Zefan 已提交
4421 4422 4423 4424
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4425 4426 4427 4428
 */
int __init cgroup_init_early(void)
{
	int i;
4429
	atomic_set(&init_css_set.refcount, 1);
4430 4431
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4432
	INIT_HLIST_NODE(&init_css_set.hlist);
4433
	css_set_count = 1;
4434
	init_cgroup_root(&rootnode);
4435 4436 4437 4438
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4439
	init_css_set_link.cgrp = dummytop;
4440
	list_add(&init_css_set_link.cgrp_link_list,
4441 4442 4443
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4444

4445 4446 4447
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

B
Ben Blum 已提交
4448 4449
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4450 4451 4452 4453 4454 4455 4456
		struct cgroup_subsys *ss = subsys[i];

		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
		BUG_ON(!ss->create);
		BUG_ON(!ss->destroy);
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4457
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4469 4470 4471 4472
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4473 4474 4475 4476 4477
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4478
	struct hlist_head *hhead;
4479 4480 4481 4482

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4483

B
Ben Blum 已提交
4484 4485
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4486 4487 4488
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4489
		if (ss->use_id)
4490
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4491 4492
	}

4493 4494 4495
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
4496
	BUG_ON(!init_root_id(&rootnode));
4497 4498 4499 4500 4501 4502 4503

	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
	if (!cgroup_kobj) {
		err = -ENOMEM;
		goto out;
	}

4504
	err = register_filesystem(&cgroup_fs_type);
4505 4506
	if (err < 0) {
		kobject_put(cgroup_kobj);
4507
		goto out;
4508
	}
4509

L
Li Zefan 已提交
4510
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4511

4512
out:
4513 4514 4515
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4516 4517
	return err;
}
4518

4519 4520 4521 4522 4523 4524
/*
 * 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,
4525
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554
 *    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 */
static int proc_cgroup_show(struct seq_file *m, void *v)
{
	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);

4555
	for_each_active_root(root) {
4556
		struct cgroup_subsys *ss;
4557
		struct cgroup *cgrp;
4558 4559
		int count = 0;

4560
		seq_printf(m, "%d:", root->hierarchy_id);
4561 4562
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4563 4564 4565
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4566
		seq_putc(m, ':');
4567
		cgrp = task_cgroup_from_root(tsk, root);
4568
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589
		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;
}

static int cgroup_open(struct inode *inode, struct file *file)
{
	struct pid *pid = PROC_I(inode)->pid;
	return single_open(file, proc_cgroup_show, pid);
}

4590
const struct file_operations proc_cgroup_operations = {
4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601
	.open		= cgroup_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

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

4602
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4603 4604 4605 4606 4607
	/*
	 * 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.
	 */
4608 4609 4610
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4611 4612
		if (ss == NULL)
			continue;
4613 4614
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4615
			   ss->root->number_of_cgroups, !ss->disabled);
4616 4617 4618 4619 4620 4621 4622
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4623
	return single_open(file, proc_cgroupstats_show, NULL);
4624 4625
}

4626
static const struct file_operations proc_cgroupstats_operations = {
4627 4628 4629 4630 4631 4632
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4633 4634
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4635
 * @child: pointer to task_struct of forking parent process.
4636 4637 4638 4639 4640
 *
 * 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
4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651
 * it was not made under the protection of RCU, cgroup_mutex or
 * threadgroup_change_begin(), so it 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.
 *
 * Outside the pointer validity we also need to process the css_set
 * inheritance between threadgoup_change_begin() and
 * threadgoup_change_end(), this way there is no leak in any process
 * wide migration performed by cgroup_attach_proc() that could otherwise
 * miss a thread because it is too early or too late in the fork stage.
4652 4653 4654 4655 4656 4657
 *
 * 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)
{
4658 4659 4660 4661 4662 4663
	/*
	 * We don't need to task_lock() current because current->cgroups
	 * can't be changed concurrently here. The parent obviously hasn't
	 * exited and called cgroup_exit(), and we are synchronized against
	 * cgroup migration through threadgroup_change_begin().
	 */
4664 4665 4666
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	INIT_LIST_HEAD(&child->cg_list);
4667 4668 4669
}

/**
L
Li Zefan 已提交
4670 4671 4672 4673 4674 4675
 * cgroup_fork_callbacks - run fork callbacks
 * @child: the new task
 *
 * Called on a new task very soon before adding it to the
 * tasklist. No need to take any locks since no-one can
 * be operating on this task.
4676 4677 4678 4679 4680
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
B
Ben Blum 已提交
4681 4682 4683 4684 4685 4686
		/*
		 * forkexit callbacks are only supported for builtin
		 * subsystems, and the builtin section of the subsys array is
		 * immutable, so we don't need to lock the subsys array here.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4687 4688
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
4689
				ss->fork(child);
4690 4691 4692 4693
		}
	}
}

4694
/**
L
Li Zefan 已提交
4695 4696 4697 4698 4699 4700 4701 4702
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
 * Adds the task to the list running through its css_set if necessary.
 * 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.
 */
4703 4704
void cgroup_post_fork(struct task_struct *child)
{
4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715
	/*
	 * 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.
	 */
4716 4717
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728
		if (list_empty(&child->cg_list)) {
			/*
			 * It's safe to use child->cgroups without task_lock()
			 * here because we are protected through
			 * threadgroup_change_begin() against concurrent
			 * css_set change in cgroup_task_migrate(). Also
			 * the task can't exit at that point until
			 * wake_up_new_task() is called, so we are protected
			 * against cgroup_exit() setting child->cgroup to
			 * init_css_set.
			 */
4729
			list_add(&child->cg_list, &child->cgroups->tasks);
4730
		}
4731 4732 4733
		write_unlock(&css_set_lock);
	}
}
4734 4735 4736
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4737
 * @run_callback: run exit callbacks?
4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765
 *
 * 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,
4766 4767
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4768 4769 4770
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4771
	struct css_set *cg;
4772
	int i;
4773 4774 4775 4776 4777 4778 4779 4780 4781

	/*
	 * 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))
4782
			list_del_init(&tsk->cg_list);
4783 4784 4785
		write_unlock(&css_set_lock);
	}

4786 4787
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4788 4789
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801

	if (run_callbacks && need_forkexit_callback) {
		/*
		 * modular subsystems can't use callbacks, so no need to lock
		 * the subsys array
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
4802
				ss->exit(cgrp, old_cgrp, tsk);
4803 4804 4805
			}
		}
	}
4806
	task_unlock(tsk);
4807

4808
	if (cg)
4809
		put_css_set_taskexit(cg);
4810
}
4811

L
Li Zefan 已提交
4812
/**
4813
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
4814
 * @cgrp: the cgroup in question
4815
 * @task: the task in question
L
Li Zefan 已提交
4816
 *
4817 4818
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
4819 4820 4821 4822 4823 4824
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
4825
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4826 4827 4828 4829
{
	int ret;
	struct cgroup *target;

4830
	if (cgrp == dummytop)
4831 4832
		return 1;

4833
	target = task_cgroup_from_root(task, cgrp->root);
4834 4835 4836
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
4837 4838
	return ret;
}
4839

4840
static void check_for_release(struct cgroup *cgrp)
4841 4842 4843
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
4844 4845
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4846 4847 4848 4849
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
4850
		raw_spin_lock(&release_list_lock);
4851 4852 4853
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
4854 4855
			need_schedule_work = 1;
		}
4856
		raw_spin_unlock(&release_list_lock);
4857 4858 4859 4860 4861
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

4862
/* Caller must verify that the css is not for root cgroup */
4863 4864
bool __css_tryget(struct cgroup_subsys_state *css)
{
T
Tejun Heo 已提交
4865 4866
	while (true) {
		int t, v;
4867

T
Tejun Heo 已提交
4868 4869 4870
		v = css_refcnt(css);
		t = atomic_cmpxchg(&css->refcnt, v, v + 1);
		if (likely(t == v))
4871
			return true;
T
Tejun Heo 已提交
4872 4873
		else if (t < 0)
			return false;
4874
		cpu_relax();
T
Tejun Heo 已提交
4875
	}
4876 4877 4878 4879 4880
}
EXPORT_SYMBOL_GPL(__css_tryget);

/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
4881
{
4882
	struct cgroup *cgrp = css->cgroup;
4883
	int v;
4884

4885
	rcu_read_lock();
4886 4887 4888
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));

	switch (v) {
4889
	case 1:
4890 4891 4892 4893
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
4894
		cgroup_wakeup_rmdir_waiter(cgrp);
4895 4896
		break;
	case 0:
4897
		schedule_work(&css->dput_work);
4898
		break;
4899 4900 4901
	}
	rcu_read_unlock();
}
B
Ben Blum 已提交
4902
EXPORT_SYMBOL_GPL(__css_put);
4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930

/*
 * 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);
4931
	raw_spin_lock(&release_list_lock);
4932 4933 4934
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
4935
		char *pathbuf = NULL, *agentbuf = NULL;
4936
		struct cgroup *cgrp = list_entry(release_list.next,
4937 4938
						    struct cgroup,
						    release_list);
4939
		list_del_init(&cgrp->release_list);
4940
		raw_spin_unlock(&release_list_lock);
4941
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4942 4943 4944 4945 4946 4947 4948
		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;
4949 4950

		i = 0;
4951 4952
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966
		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);
4967 4968 4969
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
4970
		raw_spin_lock(&release_list_lock);
4971
	}
4972
	raw_spin_unlock(&release_list_lock);
4973 4974
	mutex_unlock(&cgroup_mutex);
}
4975 4976 4977 4978 4979 4980 4981 4982 4983

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
B
Ben Blum 已提交
4984 4985 4986 4987 4988
		/*
		 * cgroup_disable, being at boot time, can't know about module
		 * subsystems, so we don't worry about them.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001
			struct cgroup_subsys *ss = subsys[i];

			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
5002 5003 5004 5005 5006 5007 5008 5009 5010 5011

/*
 * 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)
{
5012 5013 5014 5015 5016 5017 5018
	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.
	 */
5019
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5020 5021 5022 5023 5024

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5025
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5026 5027 5028

unsigned short css_depth(struct cgroup_subsys_state *css)
{
5029 5030
	struct css_id *cssid;

5031
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5032 5033 5034 5035 5036

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
5037
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
5038

5039 5040 5041 5042 5043 5044
/**
 *  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
5045
 * this function reads css->id, the caller must hold rcu_read_lock().
5046 5047 5048 5049 5050 5051
 * 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
5052
bool css_is_ancestor(struct cgroup_subsys_state *child,
5053
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5054
{
5055 5056
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5057

5058
	child_id  = rcu_dereference(child->id);
5059 5060
	if (!child_id)
		return false;
5061
	root_id = rcu_dereference(root->id);
5062 5063 5064 5065 5066 5067 5068
	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
5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081
}

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);
5082
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5083
	idr_remove(&ss->idr, id->id);
5084
	spin_unlock(&ss->id_lock);
5085
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5086
}
B
Ben Blum 已提交
5087
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109

/*
 * 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;
	int myid, error, size;

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
	/* get id */
	if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
		error = -ENOMEM;
		goto err_out;
	}
5110
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5111 5112
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5113
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127

	/* Returns error when there are no free spaces for new ID.*/
	if (error) {
		error = -ENOSPC;
		goto err_out;
	}
	if (myid > CSS_ID_MAX)
		goto remove_idr;

	newid->id = myid;
	newid->depth = depth;
	return newid;
remove_idr:
	error = -ENOSPC;
5128
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5129
	idr_remove(&ss->idr, myid);
5130
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5131 5132 5133 5134 5135 5136
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

5137 5138
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5139 5140 5141
{
	struct css_id *newid;

5142
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159
	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;
5160
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5161 5162 5163 5164 5165

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5166
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203

	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
5204
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229

/**
 * css_get_next - lookup next cgroup under specified hierarchy.
 * @ss: pointer to subsystem
 * @id: current position of iteration.
 * @root: pointer to css. search tree under this.
 * @foundid: position of found object.
 *
 * Search next css under the specified hierarchy of rootid. Calling under
 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
 */
struct cgroup_subsys_state *
css_get_next(struct cgroup_subsys *ss, int id,
	     struct cgroup_subsys_state *root, int *foundid)
{
	struct cgroup_subsys_state *ret = NULL;
	struct css_id *tmp;
	int tmpid;
	int rootid = css_id(root);
	int depth = css_depth(root);

	if (!rootid)
		return NULL;

	BUG_ON(!ss->use_id);
5230 5231
	WARN_ON_ONCE(!rcu_read_lock_held());

K
KAMEZAWA Hiroyuki 已提交
5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254
	/* fill start point for scan */
	tmpid = id;
	while (1) {
		/*
		 * scan next entry from bitmap(tree), tmpid is updated after
		 * idr_get_next().
		 */
		tmp = idr_get_next(&ss->idr, &tmpid);
		if (!tmp)
			break;
		if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
			ret = rcu_dereference(tmp->css);
			if (ret) {
				*foundid = tmpid;
				break;
			}
		}
		/* continue to scan from next id */
		tmpid = tmpid + 1;
	}
	return ret;
}

S
Stephane Eranian 已提交
5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277
/*
 * 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;

	inode = f->f_dentry->d_inode;
	/* 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);
}

5278
#ifdef CONFIG_CGROUP_DEBUG
5279
static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5280 5281 5282 5283 5284 5285 5286 5287 5288
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5289
static void debug_destroy(struct cgroup *cont)
5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319
{
	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;
}

5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337
static int current_css_set_cg_links_read(struct cgroup *cont,
					 struct cftype *cft,
					 struct seq_file *seq)
{
	struct cg_cgroup_link *link;
	struct css_set *cg;

	read_lock(&css_set_lock);
	rcu_read_lock();
	cg = rcu_dereference(current->cgroups);
	list_for_each_entry(link, &cg->cg_links, cg_link_list) {
		struct cgroup *c = link->cgrp;
		const char *name;

		if (c->dentry)
			name = c->dentry->d_name.name;
		else
			name = "?";
5338 5339
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372
	}
	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)
{
	struct cg_cgroup_link *link;

	read_lock(&css_set_lock);
	list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
		struct css_set *cg = link->cg;
		struct task_struct *task;
		int count = 0;
		seq_printf(seq, "css_set %p\n", cg);
		list_for_each_entry(task, &cg->tasks, cg_list) {
			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;
}

5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397
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,
	},

5398 5399 5400 5401 5402 5403 5404 5405 5406 5407
	{
		.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,
	},

5408 5409 5410 5411 5412
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5413 5414
	{ }	/* terminate */
};
5415 5416 5417 5418 5419 5420

struct cgroup_subsys debug_subsys = {
	.name = "debug",
	.create = debug_create,
	.destroy = debug_destroy,
	.subsys_id = debug_subsys_id,
5421
	.base_cftypes = debug_files,
5422 5423
};
#endif /* CONFIG_CGROUP_DEBUG */