summaryrefslogtreecommitdiffstats
path: root/drivers/xen/balloon.c
blob: 097ba02ac80979663c0c7b243859b1392dbf1251 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
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
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
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
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
/******************************************************************************
 * balloon.c
 *
 * Xen balloon driver - enables returning/claiming memory to/from Xen.
 *
 * Copyright (c) 2003, B Dragovic
 * Copyright (c) 2003-2004, M Williamson, K Fraser
 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/sysdev.h>

#include <asm/xen/hypervisor.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/tlb.h>

#include <xen/interface/memory.h>
#include <xen/balloon.h>
#include <xen/xenbus.h>
#include <xen/features.h>
#include <xen/page.h>

#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))

#define BALLOON_CLASS_NAME "memory"

struct balloon_stats {
	/* We aim for 'current allocation' == 'target allocation'. */
	unsigned long current_pages;
	unsigned long target_pages;
	/* We may hit the hard limit in Xen. If we do then we remember it. */
	unsigned long hard_limit;
	/*
	 * Drivers may alter the memory reservation independently, but they
	 * must inform the balloon driver so we avoid hitting the hard limit.
	 */
	unsigned long driver_pages;
	/* Number of pages in high- and low-memory balloons. */
	unsigned long balloon_low;
	unsigned long balloon_high;
};

static DEFINE_MUTEX(balloon_mutex);

static struct sys_device balloon_sysdev;

static int register_balloon(struct sys_device *sysdev);

/*
 * Protects atomic reservation decrease/increase against concurrent increases.
 * Also protects non-atomic updates of current_pages and driver_pages, and
 * balloon lists.
 */
static DEFINE_SPINLOCK(balloon_lock);

static struct balloon_stats balloon_stats;

/* We increase/decrease in batches which fit in a page */
static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];

/* VM /proc information for memory */
extern unsigned long totalram_pages;

#ifdef CONFIG_HIGHMEM
extern unsigned long totalhigh_pages;
#define inc_totalhigh_pages() (totalhigh_pages++)
#define dec_totalhigh_pages() (totalhigh_pages--)
#else
#define inc_totalhigh_pages() do {} while(0)
#define dec_totalhigh_pages() do {} while(0)
#endif

/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);

/* Main work function, always executed in process context. */
static void balloon_process(struct work_struct *work);
static DECLARE_WORK(balloon_worker, balloon_process);
static struct timer_list balloon_timer;

/* When ballooning out (allocating memory to return to Xen) we don't really
   want the kernel to try too hard since that can trigger the oom killer. */
#define GFP_BALLOON \
	(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)

static void scrub_page(struct page *page)
{
#ifdef CONFIG_XEN_SCRUB_PAGES
	if (PageHighMem(page)) {
		void *v = kmap(page);
		clear_page(v);
		kunmap(v);
	} else {
		void *v = page_address(page);
		clear_page(v);
	}
#endif
}

/* balloon_append: add the given page to the balloon. */
static void balloon_append(struct page *page)
{
	/* Lowmem is re-populated first, so highmem pages go at list tail. */
	if (PageHighMem(page)) {
		list_add_tail(&page->lru, &ballooned_pages);
		balloon_stats.balloon_high++;
		dec_totalhigh_pages();
	} else {
		list_add(&page->lru, &ballooned_pages);
		balloon_stats.balloon_low++;
	}
}

/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(void)
{
	struct page *page;

	if (list_empty(&ballooned_pages))
		return NULL;

	page = list_entry(ballooned_pages.next, struct page, lru);
	list_del(&page->lru);

	if (PageHighMem(page)) {
		balloon_stats.balloon_high--;
		inc_totalhigh_pages();
	}
	else
		balloon_stats.balloon_low--;

	return page;
}

static struct page *balloon_first_page(void)
{
	if (list_empty(&ballooned_pages))
		return NULL;
	return list_entry(ballooned_pages.next, struct page, lru);
}

static struct page *balloon_next_page(struct page *page)
{
	struct list_head *next = page->lru.next;
	if (next == &ballooned_pages)
		return NULL;
	return list_entry(next, struct page, lru);
}

static void balloon_alarm(unsigned long unused)
{
	schedule_work(&balloon_worker);
}

static unsigned long current_target(void)
{
	unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);

	target = min(target,
		     balloon_stats.current_pages +
		     balloon_stats.balloon_low +
		     balloon_stats.balloon_high);

	return target;
}

static int increase_reservation(unsigned long nr_pages)
{
	unsigned long  pfn, i, flags;
	struct page   *page;
	long           rc;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	spin_lock_irqsave(&balloon_lock, flags);

	page = balloon_first_page();
	for (i = 0; i < nr_pages; i++) {
		BUG_ON(page == NULL);
		frame_list[i] = page_to_pfn(page);;
		page = balloon_next_page(page);
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents   = nr_pages;
	rc = HYPERVISOR_memory_op(
		XENMEM_populate_physmap, &reservation);
	if (rc < nr_pages) {
		if (rc > 0) {
			int ret;

			/* We hit the Xen hard limit: reprobe. */
			reservation.nr_extents = rc;
			ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
					&reservation);
			BUG_ON(ret != rc);
		}
		if (rc >= 0)
			balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
						    balloon_stats.driver_pages);
		goto out;
	}

	for (i = 0; i < nr_pages; i++) {
		page = balloon_retrieve();
		BUG_ON(page == NULL);

		pfn = page_to_pfn(page);
		BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
		       phys_to_machine_mapping_valid(pfn));

		set_phys_to_machine(pfn, frame_list[i]);

		/* Link back into the page tables if not highmem. */
		if (pfn < max_low_pfn) {
			int ret;
			ret = HYPERVISOR_update_va_mapping(
				(unsigned long)__va(pfn << PAGE_SHIFT),
				mfn_pte(frame_list[i], PAGE_KERNEL),
				0);
			BUG_ON(ret);
		}

		/* Relinquish the page back to the allocator. */
		ClearPageReserved(page);
		init_page_count(page);
		__free_page(page);
	}

	balloon_stats.current_pages += nr_pages;
	totalram_pages = balloon_stats.current_pages;

 out:
	spin_unlock_irqrestore(&balloon_lock, flags);

	return 0;
}

static int decrease_reservation(unsigned long nr_pages)
{
	unsigned long  pfn, i, flags;
	struct page   *page;
	int            need_sleep = 0;
	int ret;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	for (i = 0; i < nr_pages; i++) {
		if ((page = alloc_page(GFP_BALLOON)) == NULL) {
			nr_pages = i;
			need_sleep = 1;
			break;
		}

		pfn = page_to_pfn(page);
		frame_list[i] = pfn_to_mfn(pfn);

		scrub_page(page);
	}

	/* Ensure that ballooned highmem pages don't have kmaps. */
	kmap_flush_unused();
	flush_tlb_all();

	spin_lock_irqsave(&balloon_lock, flags);

	/* No more mappings: invalidate P2M and add to balloon. */
	for (i = 0; i < nr_pages; i++) {
		pfn = mfn_to_pfn(frame_list[i]);
		set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
		balloon_append(pfn_to_page(pfn));
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents   = nr_pages;
	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	BUG_ON(ret != nr_pages);

	balloon_stats.current_pages -= nr_pages;
	totalram_pages = balloon_stats.current_pages;

	spin_unlock_irqrestore(&balloon_lock, flags);

	return need_sleep;
}

/*
 * We avoid multiple worker processes conflicting via the balloon mutex.
 * We may of course race updates of the target counts (which are protected
 * by the balloon lock), or with changes to the Xen hard limit, but we will
 * recover from these in time.
 */
static void balloon_process(struct work_struct *work)
{
	int need_sleep = 0;
	long credit;

	mutex_lock(&balloon_mutex);

	do {
		credit = current_target() - balloon_stats.current_pages;
		if (credit > 0)
			need_sleep = (increase_reservation(credit) != 0);
		if (credit < 0)
			need_sleep = (decrease_reservation(-credit) != 0);

#ifndef CONFIG_PREEMPT
		if (need_resched())
			schedule();
#endif
	} while ((credit != 0) && !need_sleep);

	/* Schedule more work if there is some still to be done. */
	if (current_target() != balloon_stats.current_pages)
		mod_timer(&balloon_timer, jiffies + HZ);

	mutex_unlock(&balloon_mutex);
}

/* Resets the Xen limit, sets new target, and kicks off processing. */
void balloon_set_new_target(unsigned long target)
{
	/* No need for lock. Not read-modify-write updates. */
	balloon_stats.hard_limit   = ~0UL;
	balloon_stats.target_pages = target;
	schedule_work(&balloon_worker);
}

static struct xenbus_watch target_watch =
{
	.node = "memory/target"
};

/* React to a change in the target key */
static void watch_target(struct xenbus_watch *watch,
			 const char **vec, unsigned int len)
{
	unsigned long long new_target;
	int err;

	err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
	if (err != 1) {
		/* This is ok (for domain0 at least) - so just return */
		return;
	}

	/* The given memory/target value is in KiB, so it needs converting to
	 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
	 */
	balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
}

static int balloon_init_watcher(struct notifier_block *notifier,
				unsigned long event,
				void *data)
{
	int err;

	err = register_xenbus_watch(&target_watch);
	if (err)
		printk(KERN_ERR "Failed to set balloon watcher\n");

	return NOTIFY_DONE;
}

static struct notifier_block xenstore_notifier;

static int __init balloon_init(void)
{
	unsigned long pfn;
	struct page *page;

	if (!is_running_on_xen())
		return -ENODEV;

	pr_info("xen_balloon: Initialising balloon driver.\n");

	balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
	totalram_pages   = balloon_stats.current_pages;
	balloon_stats.target_pages  = balloon_stats.current_pages;
	balloon_stats.balloon_low   = 0;
	balloon_stats.balloon_high  = 0;
	balloon_stats.driver_pages  = 0UL;
	balloon_stats.hard_limit    = ~0UL;

	init_timer(&balloon_timer);
	balloon_timer.data = 0;
	balloon_timer.function = balloon_alarm;

	register_balloon(&balloon_sysdev);

	/* Initialise the balloon with excess memory space. */
	for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
		page = pfn_to_page(pfn);
		if (!PageReserved(page))
			balloon_append(page);
	}

	target_watch.callback = watch_target;
	xenstore_notifier.notifier_call = balloon_init_watcher;

	register_xenstore_notifier(&xenstore_notifier);

	return 0;
}

subsys_initcall(balloon_init);

static void balloon_exit(void)
{
    /* XXX - release balloon here */
    return;
}

module_exit(balloon_exit);

static void balloon_update_driver_allowance(long delta)
{
	unsigned long flags;

	spin_lock_irqsave(&balloon_lock, flags);
	balloon_stats.driver_pages += delta;
	spin_unlock_irqrestore(&balloon_lock, flags);
}

static int dealloc_pte_fn(
	pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
{
	unsigned long mfn = pte_mfn(*pte);
	int ret;
	struct xen_memory_reservation reservation = {
		.nr_extents   = 1,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};
	set_xen_guest_handle(reservation.extent_start, &mfn);
	set_pte_at(&init_mm, addr, pte, __pte_ma(0ull));
	set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	BUG_ON(ret != 1);
	return 0;
}

static struct page **alloc_empty_pages_and_pagevec(int nr_pages)
{
	unsigned long vaddr, flags;
	struct page *page, **pagevec;
	int i, ret;

	pagevec = kmalloc(sizeof(page) * nr_pages, GFP_KERNEL);
	if (pagevec == NULL)
		return NULL;

	for (i = 0; i < nr_pages; i++) {
		page = pagevec[i] = alloc_page(GFP_KERNEL);
		if (page == NULL)
			goto err;

		vaddr = (unsigned long)page_address(page);

		scrub_page(page);

		spin_lock_irqsave(&balloon_lock, flags);

		if (xen_feature(XENFEAT_auto_translated_physmap)) {
			unsigned long gmfn = page_to_pfn(page);
			struct xen_memory_reservation reservation = {
				.nr_extents   = 1,
				.extent_order = 0,
				.domid        = DOMID_SELF
			};
			set_xen_guest_handle(reservation.extent_start, &gmfn);
			ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
						   &reservation);
			if (ret == 1)
				ret = 0; /* success */
		} else {
			ret = apply_to_page_range(&init_mm, vaddr, PAGE_SIZE,
						  dealloc_pte_fn, NULL);
		}

		if (ret != 0) {
			spin_unlock_irqrestore(&balloon_lock, flags);
			__free_page(page);
			goto err;
		}

		totalram_pages = --balloon_stats.current_pages;

		spin_unlock_irqrestore(&balloon_lock, flags);
	}

 out:
	schedule_work(&balloon_worker);
	flush_tlb_all();
	return pagevec;

 err:
	spin_lock_irqsave(&balloon_lock, flags);
	while (--i >= 0)
		balloon_append(pagevec[i]);
	spin_unlock_irqrestore(&balloon_lock, flags);
	kfree(pagevec);
	pagevec = NULL;
	goto out;
}

static void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
{
	unsigned long flags;
	int i;

	if (pagevec == NULL)
		return;

	spin_lock_irqsave(&balloon_lock, flags);
	for (i = 0; i < nr_pages; i++) {
		BUG_ON(page_count(pagevec[i]) != 1);
		balloon_append(pagevec[i]);
	}
	spin_unlock_irqrestore(&balloon_lock, flags);

	kfree(pagevec);

	schedule_work(&balloon_worker);
}

static void balloon_release_driver_page(struct page *page)
{
	unsigned long flags;

	spin_lock_irqsave(&balloon_lock, flags);
	balloon_append(page);
	balloon_stats.driver_pages--;
	spin_unlock_irqrestore(&balloon_lock, flags);

	schedule_work(&balloon_worker);
}


#define BALLOON_SHOW(name, format, args...)			\
	static ssize_t show_##name(struct sys_device *dev,	\
				   char *buf)			\
	{							\
		return sprintf(buf, format, ##args);		\
	}							\
	static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)

BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
BALLOON_SHOW(hard_limit_kb,
	     (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
	     (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));

static ssize_t show_target_kb(struct sys_device *dev, char *buf)
{
	return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
}

static ssize_t store_target_kb(struct sys_device *dev,
			       const char *buf,
			       size_t count)
{
	char memstring[64], *endchar;
	unsigned long long target_bytes;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (count <= 1)
		return -EBADMSG; /* runt */
	if (count > sizeof(memstring))
		return -EFBIG;   /* too long */
	strcpy(memstring, buf);

	target_bytes = memparse(memstring, &endchar);
	balloon_set_new_target(target_bytes >> PAGE_SHIFT);

	return count;
}

static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
		   show_target_kb, store_target_kb);

static struct sysdev_attribute *balloon_attrs[] = {
	&attr_target_kb,
};

static struct attribute *balloon_info_attrs[] = {
	&attr_current_kb.attr,
	&attr_low_kb.attr,
	&attr_high_kb.attr,
	&attr_hard_limit_kb.attr,
	&attr_driver_kb.attr,
	NULL
};

static struct attribute_group balloon_info_group = {
	.name = "info",
	.attrs = balloon_info_attrs,
};

static struct sysdev_class balloon_sysdev_class = {
	.name = BALLOON_CLASS_NAME,
};

static int register_balloon(struct sys_device *sysdev)
{
	int i, error;

	error = sysdev_class_register(&balloon_sysdev_class);
	if (error)
		return error;

	sysdev->id = 0;
	sysdev->cls = &balloon_sysdev_class;

	error = sysdev_register(sysdev);
	if (error) {
		sysdev_class_unregister(&balloon_sysdev_class);
		return error;
	}

	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
		error = sysdev_create_file(sysdev, balloon_attrs[i]);
		if (error)
			goto fail;
	}

	error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
	if (error)
		goto fail;

	return 0;

 fail:
	while (--i >= 0)
		sysdev_remove_file(sysdev, balloon_attrs[i]);
	sysdev_unregister(sysdev);
	sysdev_class_unregister(&balloon_sysdev_class);
	return error;
}

static void unregister_balloon(struct sys_device *sysdev)
{
	int i;

	sysfs_remove_group(&sysdev->kobj, &balloon_info_group);
	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++)
		sysdev_remove_file(sysdev, balloon_attrs[i]);
	sysdev_unregister(sysdev);
	sysdev_class_unregister(&balloon_sysdev_class);
}

static void balloon_sysfs_exit(void)
{
	unregister_balloon(&balloon_sysdev);
}

MODULE_LICENSE("GPL");
OpenPOWER on IntegriCloud