summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/platforms/pseries/cmm.c
blob: 91571841df8a70d0ea2520dd9c3977e6f85ccc24 (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Collaborative memory management interface.
 *
 * Copyright (C) 2008 IBM Corporation
 * Author(s): Brian King (brking@linux.vnet.ibm.com),
 */

#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/oom.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/stringify.h>
#include <linux/swap.h>
#include <linux/device.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/magic.h>
#include <linux/balloon_compaction.h>
#include <asm/firmware.h>
#include <asm/hvcall.h>
#include <asm/mmu.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
#include <linux/memory.h>
#include <asm/plpar_wrappers.h>

#include "pseries.h"

#define CMM_DRIVER_VERSION	"1.0.0"
#define CMM_DEFAULT_DELAY	1
#define CMM_HOTPLUG_DELAY	5
#define CMM_DEBUG			0
#define CMM_DISABLE		0
#define CMM_OOM_KB		1024
#define CMM_MIN_MEM_MB		256
#define KB2PAGES(_p)		((_p)>>(PAGE_SHIFT-10))
#define PAGES2KB(_p)		((_p)<<(PAGE_SHIFT-10))

#define CMM_MEM_HOTPLUG_PRI	1

static unsigned int delay = CMM_DEFAULT_DELAY;
static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
static unsigned int oom_kb = CMM_OOM_KB;
static unsigned int cmm_debug = CMM_DEBUG;
static unsigned int cmm_disabled = CMM_DISABLE;
static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
static bool __read_mostly simulate;
static unsigned long simulate_loan_target_kb;
static struct device cmm_dev;

MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>");
MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
MODULE_LICENSE("GPL");
MODULE_VERSION(CMM_DRIVER_VERSION);

module_param_named(delay, delay, uint, 0644);
MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
		 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
module_param_named(hotplug_delay, hotplug_delay, uint, 0644);
MODULE_PARM_DESC(hotplug_delay, "Delay (in seconds) after memory hotplug remove "
		 "before loaning resumes. "
		 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
module_param_named(oom_kb, oom_kb, uint, 0644);
MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
		 "[Default=" __stringify(CMM_OOM_KB) "]");
module_param_named(min_mem_mb, min_mem_mb, ulong, 0644);
MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
		 "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
module_param_named(debug, cmm_debug, uint, 0644);
MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
		 "[Default=" __stringify(CMM_DEBUG) "]");
module_param_named(simulate, simulate, bool, 0444);
MODULE_PARM_DESC(simulate, "Enable simulation mode (no communication with hw).");

#define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }

static atomic_long_t loaned_pages;
static unsigned long loaned_pages_target;
static unsigned long oom_freed_pages;

static DEFINE_MUTEX(hotplug_mutex);
static int hotplug_occurred; /* protected by the hotplug mutex */

static struct task_struct *cmm_thread_ptr;
static struct balloon_dev_info b_dev_info;

static long plpar_page_set_loaned(struct page *page)
{
	const unsigned long vpa = page_to_phys(page);
	unsigned long cmo_page_sz = cmo_get_page_size();
	long rc = 0;
	int i;

	if (unlikely(simulate))
		return 0;

	for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
		rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED, vpa + i, 0);

	for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
		plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE,
				   vpa + i - cmo_page_sz, 0);

	return rc;
}

static long plpar_page_set_active(struct page *page)
{
	const unsigned long vpa = page_to_phys(page);
	unsigned long cmo_page_sz = cmo_get_page_size();
	long rc = 0;
	int i;

	if (unlikely(simulate))
		return 0;

	for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
		rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE, vpa + i, 0);

	for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
		plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED,
				   vpa + i - cmo_page_sz, 0);

	return rc;
}

/**
 * cmm_alloc_pages - Allocate pages and mark them as loaned
 * @nr:	number of pages to allocate
 *
 * Return value:
 * 	number of pages requested to be allocated which were not
 **/
static long cmm_alloc_pages(long nr)
{
	struct page *page;
	long rc;

	cmm_dbg("Begin request for %ld pages\n", nr);

	while (nr) {
		/* Exit if a hotplug operation is in progress or occurred */
		if (mutex_trylock(&hotplug_mutex)) {
			if (hotplug_occurred) {
				mutex_unlock(&hotplug_mutex);
				break;
			}
			mutex_unlock(&hotplug_mutex);
		} else {
			break;
		}

		page = balloon_page_alloc();
		if (!page)
			break;
		rc = plpar_page_set_loaned(page);
		if (rc) {
			pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc);
			__free_page(page);
			break;
		}

		balloon_page_enqueue(&b_dev_info, page);
		atomic_long_inc(&loaned_pages);
		adjust_managed_page_count(page, -1);
		nr--;
	}

	cmm_dbg("End request with %ld pages unfulfilled\n", nr);
	return nr;
}

/**
 * cmm_free_pages - Free pages and mark them as active
 * @nr:	number of pages to free
 *
 * Return value:
 * 	number of pages requested to be freed which were not
 **/
static long cmm_free_pages(long nr)
{
	struct page *page;

	cmm_dbg("Begin free of %ld pages.\n", nr);
	while (nr) {
		page = balloon_page_dequeue(&b_dev_info);
		if (!page)
			break;
		plpar_page_set_active(page);
		adjust_managed_page_count(page, 1);
		__free_page(page);
		atomic_long_dec(&loaned_pages);
		nr--;
	}
	cmm_dbg("End request with %ld pages unfulfilled\n", nr);
	return nr;
}

/**
 * cmm_oom_notify - OOM notifier
 * @self:	notifier block struct
 * @dummy:	not used
 * @parm:	returned - number of pages freed
 *
 * Return value:
 * 	NOTIFY_OK
 **/
static int cmm_oom_notify(struct notifier_block *self,
			  unsigned long dummy, void *parm)
{
	unsigned long *freed = parm;
	long nr = KB2PAGES(oom_kb);

	cmm_dbg("OOM processing started\n");
	nr = cmm_free_pages(nr);
	loaned_pages_target = atomic_long_read(&loaned_pages);
	*freed += KB2PAGES(oom_kb) - nr;
	oom_freed_pages += KB2PAGES(oom_kb) - nr;
	cmm_dbg("OOM processing complete\n");
	return NOTIFY_OK;
}

/**
 * cmm_get_mpp - Read memory performance parameters
 *
 * Makes hcall to query the current page loan request from the hypervisor.
 *
 * Return value:
 * 	nothing
 **/
static void cmm_get_mpp(void)
{
	const long __loaned_pages = atomic_long_read(&loaned_pages);
	const long total_pages = totalram_pages() + __loaned_pages;
	int rc;
	struct hvcall_mpp_data mpp_data;
	signed long active_pages_target, page_loan_request, target;
	signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;

	if (likely(!simulate)) {
		rc = h_get_mpp(&mpp_data);
		if (rc != H_SUCCESS)
			return;
		page_loan_request = div_s64((s64)mpp_data.loan_request,
					    PAGE_SIZE);
		target = page_loan_request + __loaned_pages;
	} else {
		target = KB2PAGES(simulate_loan_target_kb);
		page_loan_request = target - __loaned_pages;
	}

	if (target < 0 || total_pages < min_mem_pages)
		target = 0;

	if (target > oom_freed_pages)
		target -= oom_freed_pages;
	else
		target = 0;

	active_pages_target = total_pages - target;

	if (min_mem_pages > active_pages_target)
		target = total_pages - min_mem_pages;

	if (target < 0)
		target = 0;

	loaned_pages_target = target;

	cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
		page_loan_request, __loaned_pages, loaned_pages_target,
		oom_freed_pages, totalram_pages());
}

static struct notifier_block cmm_oom_nb = {
	.notifier_call = cmm_oom_notify
};

/**
 * cmm_thread - CMM task thread
 * @dummy:	not used
 *
 * Return value:
 * 	0
 **/
static int cmm_thread(void *dummy)
{
	unsigned long timeleft;
	long __loaned_pages;

	while (1) {
		timeleft = msleep_interruptible(delay * 1000);

		if (kthread_should_stop() || timeleft)
			break;

		if (mutex_trylock(&hotplug_mutex)) {
			if (hotplug_occurred) {
				hotplug_occurred = 0;
				mutex_unlock(&hotplug_mutex);
				cmm_dbg("Hotplug operation has occurred, "
						"loaning activity suspended "
						"for %d seconds.\n",
						hotplug_delay);
				timeleft = msleep_interruptible(hotplug_delay *
						1000);
				if (kthread_should_stop() || timeleft)
					break;
				continue;
			}
			mutex_unlock(&hotplug_mutex);
		} else {
			cmm_dbg("Hotplug operation in progress, activity "
					"suspended\n");
			continue;
		}

		cmm_get_mpp();

		__loaned_pages = atomic_long_read(&loaned_pages);
		if (loaned_pages_target > __loaned_pages) {
			if (cmm_alloc_pages(loaned_pages_target - __loaned_pages))
				loaned_pages_target = __loaned_pages;
		} else if (loaned_pages_target < __loaned_pages)
			cmm_free_pages(__loaned_pages - loaned_pages_target);
	}
	return 0;
}

#define CMM_SHOW(name, format, args...)			\
	static ssize_t show_##name(struct device *dev,	\
				   struct device_attribute *attr,	\
				   char *buf)			\
	{							\
		return sprintf(buf, format, ##args);		\
	}							\
	static DEVICE_ATTR(name, 0444, show_##name, NULL)

CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(atomic_long_read(&loaned_pages)));
CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));

static ssize_t show_oom_pages(struct device *dev,
			      struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages));
}

static ssize_t store_oom_pages(struct device *dev,
			       struct device_attribute *attr,
			       const char *buf, size_t count)
{
	unsigned long val = simple_strtoul (buf, NULL, 10);

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (val != 0)
		return -EBADMSG;

	oom_freed_pages = 0;
	return count;
}

static DEVICE_ATTR(oom_freed_kb, 0644,
		   show_oom_pages, store_oom_pages);

static struct device_attribute *cmm_attrs[] = {
	&dev_attr_loaned_kb,
	&dev_attr_loaned_target_kb,
	&dev_attr_oom_freed_kb,
};

static DEVICE_ULONG_ATTR(simulate_loan_target_kb, 0644,
			 simulate_loan_target_kb);

static struct bus_type cmm_subsys = {
	.name = "cmm",
	.dev_name = "cmm",
};

static void cmm_release_device(struct device *dev)
{
}

/**
 * cmm_sysfs_register - Register with sysfs
 *
 * Return value:
 * 	0 on success / other on failure
 **/
static int cmm_sysfs_register(struct device *dev)
{
	int i, rc;

	if ((rc = subsys_system_register(&cmm_subsys, NULL)))
		return rc;

	dev->id = 0;
	dev->bus = &cmm_subsys;
	dev->release = cmm_release_device;

	if ((rc = device_register(dev)))
		goto subsys_unregister;

	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
		if ((rc = device_create_file(dev, cmm_attrs[i])))
			goto fail;
	}

	if (!simulate)
		return 0;
	rc = device_create_file(dev, &dev_attr_simulate_loan_target_kb.attr);
	if (rc)
		goto fail;
	return 0;

fail:
	while (--i >= 0)
		device_remove_file(dev, cmm_attrs[i]);
	device_unregister(dev);
subsys_unregister:
	bus_unregister(&cmm_subsys);
	return rc;
}

/**
 * cmm_unregister_sysfs - Unregister from sysfs
 *
 **/
static void cmm_unregister_sysfs(struct device *dev)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
		device_remove_file(dev, cmm_attrs[i]);
	device_unregister(dev);
	bus_unregister(&cmm_subsys);
}

/**
 * cmm_reboot_notifier - Make sure pages are not still marked as "loaned"
 *
 **/
static int cmm_reboot_notifier(struct notifier_block *nb,
			       unsigned long action, void *unused)
{
	if (action == SYS_RESTART) {
		if (cmm_thread_ptr)
			kthread_stop(cmm_thread_ptr);
		cmm_thread_ptr = NULL;
		cmm_free_pages(atomic_long_read(&loaned_pages));
	}
	return NOTIFY_DONE;
}

static struct notifier_block cmm_reboot_nb = {
	.notifier_call = cmm_reboot_notifier,
};

/**
 * cmm_memory_cb - Handle memory hotplug notifier calls
 * @self:	notifier block struct
 * @action:	action to take
 * @arg:	struct memory_notify data for handler
 *
 * Return value:
 *	NOTIFY_OK or notifier error based on subfunction return value
 *
 **/
static int cmm_memory_cb(struct notifier_block *self,
			unsigned long action, void *arg)
{
	int ret = 0;

	switch (action) {
	case MEM_GOING_OFFLINE:
		mutex_lock(&hotplug_mutex);
		hotplug_occurred = 1;
		break;
	case MEM_OFFLINE:
	case MEM_CANCEL_OFFLINE:
		mutex_unlock(&hotplug_mutex);
		cmm_dbg("Memory offline operation complete.\n");
		break;
	case MEM_GOING_ONLINE:
	case MEM_ONLINE:
	case MEM_CANCEL_ONLINE:
		break;
	}

	return notifier_from_errno(ret);
}

static struct notifier_block cmm_mem_nb = {
	.notifier_call = cmm_memory_cb,
	.priority = CMM_MEM_HOTPLUG_PRI
};

#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;

static int cmm_init_fs_context(struct fs_context *fc)
{
	return init_pseudo(fc, PPC_CMM_MAGIC) ? 0 : -ENOMEM;
}

static struct file_system_type balloon_fs = {
	.name = "ppc-cmm",
	.init_fs_context = cmm_init_fs_context,
	.kill_sb = kill_anon_super,
};

static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
			   struct page *newpage, struct page *page,
			   enum migrate_mode mode)
{
	unsigned long flags;

	/*
	 * loan/"inflate" the newpage first.
	 *
	 * We might race against the cmm_thread who might discover after our
	 * loan request that another page is to be unloaned. However, once
	 * the cmm_thread runs again later, this error will automatically
	 * be corrected.
	 */
	if (plpar_page_set_loaned(newpage)) {
		/* Unlikely, but possible. Tell the caller not to retry now. */
		pr_err_ratelimited("%s: Cannot set page to loaned.", __func__);
		return -EBUSY;
	}

	/* balloon page list reference */
	get_page(newpage);

	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
	balloon_page_insert(b_dev_info, newpage);
	balloon_page_delete(page);
	b_dev_info->isolated_pages--;
	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);

	/*
	 * activate/"deflate" the old page. We ignore any errors just like the
	 * other callers.
	 */
	plpar_page_set_active(page);

	/* balloon page list reference */
	put_page(page);

	return MIGRATEPAGE_SUCCESS;
}

static int cmm_balloon_compaction_init(void)
{
	int rc;

	balloon_devinfo_init(&b_dev_info);
	b_dev_info.migratepage = cmm_migratepage;

	balloon_mnt = kern_mount(&balloon_fs);
	if (IS_ERR(balloon_mnt)) {
		rc = PTR_ERR(balloon_mnt);
		balloon_mnt = NULL;
		return rc;
	}

	b_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
	if (IS_ERR(b_dev_info.inode)) {
		rc = PTR_ERR(b_dev_info.inode);
		b_dev_info.inode = NULL;
		kern_unmount(balloon_mnt);
		balloon_mnt = NULL;
		return rc;
	}

	b_dev_info.inode->i_mapping->a_ops = &balloon_aops;
	return 0;
}
static void cmm_balloon_compaction_deinit(void)
{
	if (b_dev_info.inode)
		iput(b_dev_info.inode);
	b_dev_info.inode = NULL;
	kern_unmount(balloon_mnt);
	balloon_mnt = NULL;
}
#else /* CONFIG_BALLOON_COMPACTION */
static int cmm_balloon_compaction_init(void)
{
	return 0;
}

static void cmm_balloon_compaction_deinit(void)
{
}
#endif /* CONFIG_BALLOON_COMPACTION */

/**
 * cmm_init - Module initialization
 *
 * Return value:
 * 	0 on success / other on failure
 **/
static int cmm_init(void)
{
	int rc;

	if (!firmware_has_feature(FW_FEATURE_CMO) && !simulate)
		return -EOPNOTSUPP;

	rc = cmm_balloon_compaction_init();
	if (rc)
		return rc;

	rc = register_oom_notifier(&cmm_oom_nb);
	if (rc < 0)
		goto out_balloon_compaction;

	if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
		goto out_oom_notifier;

	if ((rc = cmm_sysfs_register(&cmm_dev)))
		goto out_reboot_notifier;

	rc = register_memory_notifier(&cmm_mem_nb);
	if (rc)
		goto out_unregister_notifier;

	if (cmm_disabled)
		return 0;

	cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
	if (IS_ERR(cmm_thread_ptr)) {
		rc = PTR_ERR(cmm_thread_ptr);
		goto out_unregister_notifier;
	}

	return 0;
out_unregister_notifier:
	unregister_memory_notifier(&cmm_mem_nb);
	cmm_unregister_sysfs(&cmm_dev);
out_reboot_notifier:
	unregister_reboot_notifier(&cmm_reboot_nb);
out_oom_notifier:
	unregister_oom_notifier(&cmm_oom_nb);
out_balloon_compaction:
	cmm_balloon_compaction_deinit();
	return rc;
}

/**
 * cmm_exit - Module exit
 *
 * Return value:
 * 	nothing
 **/
static void cmm_exit(void)
{
	if (cmm_thread_ptr)
		kthread_stop(cmm_thread_ptr);
	unregister_oom_notifier(&cmm_oom_nb);
	unregister_reboot_notifier(&cmm_reboot_nb);
	unregister_memory_notifier(&cmm_mem_nb);
	cmm_free_pages(atomic_long_read(&loaned_pages));
	cmm_unregister_sysfs(&cmm_dev);
	cmm_balloon_compaction_deinit();
}

/**
 * cmm_set_disable - Disable/Enable CMM
 *
 * Return value:
 * 	0 on success / other on failure
 **/
static int cmm_set_disable(const char *val, const struct kernel_param *kp)
{
	int disable = simple_strtoul(val, NULL, 10);

	if (disable != 0 && disable != 1)
		return -EINVAL;

	if (disable && !cmm_disabled) {
		if (cmm_thread_ptr)
			kthread_stop(cmm_thread_ptr);
		cmm_thread_ptr = NULL;
		cmm_free_pages(atomic_long_read(&loaned_pages));
	} else if (!disable && cmm_disabled) {
		cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
		if (IS_ERR(cmm_thread_ptr))
			return PTR_ERR(cmm_thread_ptr);
	}

	cmm_disabled = disable;
	return 0;
}

module_param_call(disable, cmm_set_disable, param_get_uint,
		  &cmm_disabled, 0644);
MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
		 "[Default=" __stringify(CMM_DISABLE) "]");

module_init(cmm_init);
module_exit(cmm_exit);