summaryrefslogtreecommitdiff
path: root/mm/mlock.c
blob: efd2dd2943decfb384c36d2ab1d4a9c1cf152a66 (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
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
746
747
748
749
750
751
// SPDX-License-Identifier: GPL-2.0
/*
 *	linux/mm/mlock.c
 *
 *  (C) Copyright 1995 Linus Torvalds
 *  (C) Copyright 2002 Christoph Hellwig
 */

#include <linux/capability.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/sched/user.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/pagewalk.h>
#include <linux/mempolicy.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
#include <linux/export.h>
#include <linux/rmap.h>
#include <linux/mmzone.h>
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/secretmem.h>

#include "internal.h"

static DEFINE_PER_CPU(struct pagevec, mlock_pvec);

bool can_do_mlock(void)
{
	if (rlimit(RLIMIT_MEMLOCK) != 0)
		return true;
	if (capable(CAP_IPC_LOCK))
		return true;
	return false;
}
EXPORT_SYMBOL(can_do_mlock);

/*
 * Mlocked pages are marked with PageMlocked() flag for efficient testing
 * in vmscan and, possibly, the fault path; and to support semi-accurate
 * statistics.
 *
 * An mlocked page [PageMlocked(page)] is unevictable.  As such, it will
 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
 * The unevictable list is an LRU sibling list to the [in]active lists.
 * PageUnevictable is set to indicate the unevictable state.
 */

static struct lruvec *__mlock_page(struct page *page, struct lruvec *lruvec)
{
	/* There is nothing more we can do while it's off LRU */
	if (!TestClearPageLRU(page))
		return lruvec;

	lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

	if (unlikely(page_evictable(page))) {
		/*
		 * This is a little surprising, but quite possible:
		 * PageMlocked must have got cleared already by another CPU.
		 * Could this page be on the Unevictable LRU?  I'm not sure,
		 * but move it now if so.
		 */
		if (PageUnevictable(page)) {
			del_page_from_lru_list(page, lruvec);
			ClearPageUnevictable(page);
			add_page_to_lru_list(page, lruvec);
			__count_vm_events(UNEVICTABLE_PGRESCUED,
					  thp_nr_pages(page));
		}
		goto out;
	}

	if (PageUnevictable(page)) {
		if (PageMlocked(page))
			page->mlock_count++;
		goto out;
	}

	del_page_from_lru_list(page, lruvec);
	ClearPageActive(page);
	SetPageUnevictable(page);
	page->mlock_count = !!PageMlocked(page);
	add_page_to_lru_list(page, lruvec);
	__count_vm_events(UNEVICTABLE_PGCULLED, thp_nr_pages(page));
out:
	SetPageLRU(page);
	return lruvec;
}

static struct lruvec *__mlock_new_page(struct page *page, struct lruvec *lruvec)
{
	VM_BUG_ON_PAGE(PageLRU(page), page);

	lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

	/* As above, this is a little surprising, but possible */
	if (unlikely(page_evictable(page)))
		goto out;

	SetPageUnevictable(page);
	page->mlock_count = !!PageMlocked(page);
	__count_vm_events(UNEVICTABLE_PGCULLED, thp_nr_pages(page));
out:
	add_page_to_lru_list(page, lruvec);
	SetPageLRU(page);
	return lruvec;
}

static struct lruvec *__munlock_page(struct page *page, struct lruvec *lruvec)
{
	int nr_pages = thp_nr_pages(page);
	bool isolated = false;

	if (!TestClearPageLRU(page))
		goto munlock;

	isolated = true;
	lruvec = folio_lruvec_relock_irq(page_folio(page), lruvec);

	if (PageUnevictable(page)) {
		/* Then mlock_count is maintained, but might undercount */
		if (page->mlock_count)
			page->mlock_count--;
		if (page->mlock_count)
			goto out;
	}
	/* else assume that was the last mlock: reclaim will fix it if not */

munlock:
	if (TestClearPageMlocked(page)) {
		__mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
		if (isolated || !PageUnevictable(page))
			__count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
		else
			__count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
	}

	/* page_evictable() has to be checked *after* clearing Mlocked */
	if (isolated && PageUnevictable(page) && page_evictable(page)) {
		del_page_from_lru_list(page, lruvec);
		ClearPageUnevictable(page);
		add_page_to_lru_list(page, lruvec);
		__count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
	}
out:
	if (isolated)
		SetPageLRU(page);
	return lruvec;
}

/*
 * Flags held in the low bits of a struct page pointer on the mlock_pvec.
 */
#define LRU_PAGE 0x1
#define NEW_PAGE 0x2
static inline struct page *mlock_lru(struct page *page)
{
	return (struct page *)((unsigned long)page + LRU_PAGE);
}

static inline struct page *mlock_new(struct page *page)
{
	return (struct page *)((unsigned long)page + NEW_PAGE);
}

/*
 * mlock_pagevec() is derived from pagevec_lru_move_fn():
 * perhaps that can make use of such page pointer flags in future,
 * but for now just keep it for mlock.  We could use three separate
 * pagevecs instead, but one feels better (munlocking a full pagevec
 * does not need to drain mlocking pagevecs first).
 */
static void mlock_pagevec(struct pagevec *pvec)
{
	struct lruvec *lruvec = NULL;
	unsigned long mlock;
	struct page *page;
	int i;

	for (i = 0; i < pagevec_count(pvec); i++) {
		page = pvec->pages[i];
		mlock = (unsigned long)page & (LRU_PAGE | NEW_PAGE);
		page = (struct page *)((unsigned long)page - mlock);
		pvec->pages[i] = page;

		if (mlock & LRU_PAGE)
			lruvec = __mlock_page(page, lruvec);
		else if (mlock & NEW_PAGE)
			lruvec = __mlock_new_page(page, lruvec);
		else
			lruvec = __munlock_page(page, lruvec);
	}

	if (lruvec)
		unlock_page_lruvec_irq(lruvec);
	release_pages(pvec->pages, pvec->nr);
	pagevec_reinit(pvec);
}

void mlock_page_drain(int cpu)
{
	struct pagevec *pvec;

	pvec = &per_cpu(mlock_pvec, cpu);
	if (pagevec_count(pvec))
		mlock_pagevec(pvec);
}

bool need_mlock_page_drain(int cpu)
{
	return pagevec_count(&per_cpu(mlock_pvec, cpu));
}

/**
 * mlock_folio - mlock a folio already on (or temporarily off) LRU
 * @folio: folio to be mlocked.
 */
void mlock_folio(struct folio *folio)
{
	struct pagevec *pvec = &get_cpu_var(mlock_pvec);

	if (!folio_test_set_mlocked(folio)) {
		int nr_pages = folio_nr_pages(folio);

		zone_stat_mod_folio(folio, NR_MLOCK, nr_pages);
		__count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
	}

	folio_get(folio);
	if (!pagevec_add(pvec, mlock_lru(&folio->page)) ||
	    folio_test_large(folio) || lru_cache_disabled())
		mlock_pagevec(pvec);
	put_cpu_var(mlock_pvec);
}

/**
 * mlock_new_page - mlock a newly allocated page not yet on LRU
 * @page: page to be mlocked, either a normal page or a THP head.
 */
void mlock_new_page(struct page *page)
{
	struct pagevec *pvec = &get_cpu_var(mlock_pvec);
	int nr_pages = thp_nr_pages(page);

	SetPageMlocked(page);
	mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
	__count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);

	get_page(page);
	if (!pagevec_add(pvec, mlock_new(page)) ||
	    PageHead(page) || lru_cache_disabled())
		mlock_pagevec(pvec);
	put_cpu_var(mlock_pvec);
}

/**
 * munlock_page - munlock a page
 * @page: page to be munlocked, either a normal page or a THP head.
 */
void munlock_page(struct page *page)
{
	struct pagevec *pvec = &get_cpu_var(mlock_pvec);

	/*
	 * TestClearPageMlocked(page) must be left to __munlock_page(),
	 * which will check whether the page is multiply mlocked.
	 */

	get_page(page);
	if (!pagevec_add(pvec, page) ||
	    PageHead(page) || lru_cache_disabled())
		mlock_pagevec(pvec);
	put_cpu_var(mlock_pvec);
}

static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
			   unsigned long end, struct mm_walk *walk)

{
	struct vm_area_struct *vma = walk->vma;
	spinlock_t *ptl;
	pte_t *start_pte, *pte;
	struct page *page;

	ptl = pmd_trans_huge_lock(pmd, vma);
	if (ptl) {
		if (!pmd_present(*pmd))
			goto out;
		if (is_huge_zero_pmd(*pmd))
			goto out;
		page = pmd_page(*pmd);
		if (vma->vm_flags & VM_LOCKED)
			mlock_folio(page_folio(page));
		else
			munlock_page(page);
		goto out;
	}

	start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {
		if (!pte_present(*pte))
			continue;
		page = vm_normal_page(vma, addr, *pte);
		if (!page)
			continue;
		if (PageTransCompound(page))
			continue;
		if (vma->vm_flags & VM_LOCKED)
			mlock_folio(page_folio(page));
		else
			munlock_page(page);
	}
	pte_unmap(start_pte);
out:
	spin_unlock(ptl);
	cond_resched();
	return 0;
}

/*
 * mlock_vma_pages_range() - mlock any pages already in the range,
 *                           or munlock all pages in the range.
 * @vma - vma containing range to be mlock()ed or munlock()ed
 * @start - start address in @vma of the range
 * @end - end of range in @vma
 * @newflags - the new set of flags for @vma.
 *
 * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED;
 * called for munlock() and munlockall(), to clear VM_LOCKED from @vma.
 */
static void mlock_vma_pages_range(struct vm_area_struct *vma,
	unsigned long start, unsigned long end, vm_flags_t newflags)
{
	static const struct mm_walk_ops mlock_walk_ops = {
		.pmd_entry = mlock_pte_range,
	};

	/*
	 * There is a slight chance that concurrent page migration,
	 * or page reclaim finding a page of this now-VM_LOCKED vma,
	 * will call mlock_vma_page() and raise page's mlock_count:
	 * double counting, leaving the page unevictable indefinitely.
	 * Communicate this danger to mlock_vma_page() with VM_IO,
	 * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
	 * mmap_lock is held in write mode here, so this weird
	 * combination should not be visible to other mmap_lock users;
	 * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
	 */
	if (newflags & VM_LOCKED)
		newflags |= VM_IO;
	WRITE_ONCE(vma->vm_flags, newflags);

	lru_add_drain();
	walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
	lru_add_drain();

	if (newflags & VM_IO) {
		newflags &= ~VM_IO;
		WRITE_ONCE(vma->vm_flags, newflags);
	}
}

/*
 * mlock_fixup  - handle mlock[all]/munlock[all] requests.
 *
 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
 * munlock is a no-op.  However, for some special vmas, we go ahead and
 * populate the ptes.
 *
 * For vmas that pass the filters, merge/split as appropriate.
 */
static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
	unsigned long start, unsigned long end, vm_flags_t newflags)
{
	struct mm_struct *mm = vma->vm_mm;
	pgoff_t pgoff;
	int nr_pages;
	int ret = 0;
	vm_flags_t oldflags = vma->vm_flags;

	if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
	    is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
	    vma_is_dax(vma) || vma_is_secretmem(vma))
		/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
		goto out;

	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
			  vma->vm_file, pgoff, vma_policy(vma),
			  vma->vm_userfaultfd_ctx, anon_vma_name(vma));
	if (*prev) {
		vma = *prev;
		goto success;
	}

	if (start != vma->vm_start) {
		ret = split_vma(mm, vma, start, 1);
		if (ret)
			goto out;
	}

	if (end != vma->vm_end) {
		ret = split_vma(mm, vma, end, 0);
		if (ret)
			goto out;
	}

success:
	/*
	 * Keep track of amount of locked VM.
	 */
	nr_pages = (end - start) >> PAGE_SHIFT;
	if (!(newflags & VM_LOCKED))
		nr_pages = -nr_pages;
	else if (oldflags & VM_LOCKED)
		nr_pages = 0;
	mm->locked_vm += nr_pages;

	/*
	 * vm_flags is protected by the mmap_lock held in write mode.
	 * It's okay if try_to_unmap_one unmaps a page just after we
	 * set VM_LOCKED, populate_vma_page_range will bring it back.
	 */

	if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
		/* No work to do, and mlocking twice would be wrong */
		vma->vm_flags = newflags;
	} else {
		mlock_vma_pages_range(vma, start, end, newflags);
	}
out:
	*prev = vma;
	return ret;
}

static int apply_vma_lock_flags(unsigned long start, size_t len,
				vm_flags_t flags)
{
	unsigned long nstart, end, tmp;
	struct vm_area_struct *vma, *prev;
	int error;

	VM_BUG_ON(offset_in_page(start));
	VM_BUG_ON(len != PAGE_ALIGN(len));
	end = start + len;
	if (end < start)
		return -EINVAL;
	if (end == start)
		return 0;
	vma = find_vma(current->mm, start);
	if (!vma || vma->vm_start > start)
		return -ENOMEM;

	prev = vma->vm_prev;
	if (start > vma->vm_start)
		prev = vma;

	for (nstart = start ; ; ) {
		vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;

		newflags |= flags;

		/* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
		tmp = vma->vm_end;
		if (tmp > end)
			tmp = end;
		error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
		if (error)
			break;
		nstart = tmp;
		if (nstart < prev->vm_end)
			nstart = prev->vm_end;
		if (nstart >= end)
			break;

		vma = prev->vm_next;
		if (!vma || vma->vm_start != nstart) {
			error = -ENOMEM;
			break;
		}
	}
	return error;
}

/*
 * Go through vma areas and sum size of mlocked
 * vma pages, as return value.
 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
 * is also counted.
 * Return value: previously mlocked page counts
 */
static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
		unsigned long start, size_t len)
{
	struct vm_area_struct *vma;
	unsigned long count = 0;

	if (mm == NULL)
		mm = current->mm;

	vma = find_vma(mm, start);
	if (vma == NULL)
		return 0;

	for (; vma ; vma = vma->vm_next) {
		if (start >= vma->vm_end)
			continue;
		if (start + len <=  vma->vm_start)
			break;
		if (vma->vm_flags & VM_LOCKED) {
			if (start > vma->vm_start)
				count -= (start - vma->vm_start);
			if (start + len < vma->vm_end) {
				count += start + len - vma->vm_start;
				break;
			}
			count += vma->vm_end - vma->vm_start;
		}
	}

	return count >> PAGE_SHIFT;
}

/*
 * convert get_user_pages() return value to posix mlock() error
 */
static int __mlock_posix_error_return(long retval)
{
	if (retval == -EFAULT)
		retval = -ENOMEM;
	else if (retval == -ENOMEM)
		retval = -EAGAIN;
	return retval;
}

static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
{
	unsigned long locked;
	unsigned long lock_limit;
	int error = -ENOMEM;

	start = untagged_addr(start);

	if (!can_do_mlock())
		return -EPERM;

	len = PAGE_ALIGN(len + (offset_in_page(start)));
	start &= PAGE_MASK;

	lock_limit = rlimit(RLIMIT_MEMLOCK);
	lock_limit >>= PAGE_SHIFT;
	locked = len >> PAGE_SHIFT;

	if (mmap_write_lock_killable(current->mm))
		return -EINTR;

	locked += current->mm->locked_vm;
	if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
		/*
		 * It is possible that the regions requested intersect with
		 * previously mlocked areas, that part area in "mm->locked_vm"
		 * should not be counted to new mlock increment count. So check
		 * and adjust locked count if necessary.
		 */
		locked -= count_mm_mlocked_page_nr(current->mm,
				start, len);
	}

	/* check against resource limits */
	if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
		error = apply_vma_lock_flags(start, len, flags);

	mmap_write_unlock(current->mm);
	if (error)
		return error;

	error = __mm_populate(start, len, 0);
	if (error)
		return __mlock_posix_error_return(error);
	return 0;
}

SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
{
	return do_mlock(start, len, VM_LOCKED);
}

SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
{
	vm_flags_t vm_flags = VM_LOCKED;

	if (flags & ~MLOCK_ONFAULT)
		return -EINVAL;

	if (flags & MLOCK_ONFAULT)
		vm_flags |= VM_LOCKONFAULT;

	return do_mlock(start, len, vm_flags);
}

SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
	int ret;

	start = untagged_addr(start);

	len = PAGE_ALIGN(len + (offset_in_page(start)));
	start &= PAGE_MASK;

	if (mmap_write_lock_killable(current->mm))
		return -EINTR;
	ret = apply_vma_lock_flags(start, len, 0);
	mmap_write_unlock(current->mm);

	return ret;
}

/*
 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
 * and translate into the appropriate modifications to mm->def_flags and/or the
 * flags for all current VMAs.
 *
 * There are a couple of subtleties with this.  If mlockall() is called multiple
 * times with different flags, the values do not necessarily stack.  If mlockall
 * is called once including the MCL_FUTURE flag and then a second time without
 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
 */
static int apply_mlockall_flags(int flags)
{
	struct vm_area_struct *vma, *prev = NULL;
	vm_flags_t to_add = 0;

	current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
	if (flags & MCL_FUTURE) {
		current->mm->def_flags |= VM_LOCKED;

		if (flags & MCL_ONFAULT)
			current->mm->def_flags |= VM_LOCKONFAULT;

		if (!(flags & MCL_CURRENT))
			goto out;
	}

	if (flags & MCL_CURRENT) {
		to_add |= VM_LOCKED;
		if (flags & MCL_ONFAULT)
			to_add |= VM_LOCKONFAULT;
	}

	for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
		vm_flags_t newflags;

		newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
		newflags |= to_add;

		/* Ignore errors */
		mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
		cond_resched();
	}
out:
	return 0;
}

SYSCALL_DEFINE1(mlockall, int, flags)
{
	unsigned long lock_limit;
	int ret;

	if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
	    flags == MCL_ONFAULT)
		return -EINVAL;

	if (!can_do_mlock())
		return -EPERM;

	lock_limit = rlimit(RLIMIT_MEMLOCK);
	lock_limit >>= PAGE_SHIFT;

	if (mmap_write_lock_killable(current->mm))
		return -EINTR;

	ret = -ENOMEM;
	if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
	    capable(CAP_IPC_LOCK))
		ret = apply_mlockall_flags(flags);
	mmap_write_unlock(current->mm);
	if (!ret && (flags & MCL_CURRENT))
		mm_populate(0, TASK_SIZE);

	return ret;
}

SYSCALL_DEFINE0(munlockall)
{
	int ret;

	if (mmap_write_lock_killable(current->mm))
		return -EINTR;
	ret = apply_mlockall_flags(0);
	mmap_write_unlock(current->mm);
	return ret;
}

/*
 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 * shm segments) get accounted against the user_struct instead.
 */
static DEFINE_SPINLOCK(shmlock_user_lock);

int user_shm_lock(size_t size, struct ucounts *ucounts)
{
	unsigned long lock_limit, locked;
	long memlock;
	int allowed = 0;

	locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	lock_limit = rlimit(RLIMIT_MEMLOCK);
	if (lock_limit == RLIM_INFINITY)
		allowed = 1;
	lock_limit >>= PAGE_SHIFT;
	spin_lock(&shmlock_user_lock);
	memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);

	if (!allowed && (memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) {
		dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
		goto out;
	}
	if (!get_ucounts(ucounts)) {
		dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
		allowed = 0;
		goto out;
	}
	allowed = 1;
out:
	spin_unlock(&shmlock_user_lock);
	return allowed;
}

void user_shm_unlock(size_t size, struct ucounts *ucounts)
{
	spin_lock(&shmlock_user_lock);
	dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, (size + PAGE_SIZE - 1) >> PAGE_SHIFT);
	spin_unlock(&shmlock_user_lock);
	put_ucounts(ucounts);
}