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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/mm/mlock.c
4 *
5 * (C) Copyright 1995 Linus Torvalds
6 * (C) Copyright 2002 Christoph Hellwig
7 */
8
9#include <linux/capability.h>
10#include <linux/mman.h>
11#include <linux/mm.h>
12#include <linux/sched/user.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/pagemap.h>
16#include <linux/pagevec.h>
17#include <linux/mempolicy.h>
18#include <linux/syscalls.h>
19#include <linux/sched.h>
20#include <linux/export.h>
21#include <linux/rmap.h>
22#include <linux/mmzone.h>
23#include <linux/hugetlb.h>
24#include <linux/memcontrol.h>
25#include <linux/mm_inline.h>
26
27#include "internal.h"
28
29bool can_do_mlock(void)
30{
31 if (rlimit(RLIMIT_MEMLOCK) != 0)
32 return true;
33 if (capable(CAP_IPC_LOCK))
34 return true;
35 return false;
36}
37EXPORT_SYMBOL(can_do_mlock);
38
39/*
40 * Mlocked pages are marked with PageMlocked() flag for efficient testing
41 * in vmscan and, possibly, the fault path; and to support semi-accurate
42 * statistics.
43 *
44 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
45 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
46 * The unevictable list is an LRU sibling list to the [in]active lists.
47 * PageUnevictable is set to indicate the unevictable state.
48 *
49 * When lazy mlocking via vmscan, it is important to ensure that the
50 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
51 * may have mlocked a page that is being munlocked. So lazy mlock must take
52 * the mmap_lock for read, and verify that the vma really is locked
53 * (see mm/rmap.c).
54 */
55
56/*
57 * LRU accounting for clear_page_mlock()
58 */
59void clear_page_mlock(struct page *page)
60{
61 int nr_pages;
62
63 if (!TestClearPageMlocked(page))
64 return;
65
66 nr_pages = thp_nr_pages(page);
67 mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
68 count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
69 /*
70 * The previous TestClearPageMlocked() corresponds to the smp_mb()
71 * in __pagevec_lru_add_fn().
72 *
73 * See __pagevec_lru_add_fn for more explanation.
74 */
75 if (!isolate_lru_page(page)) {
76 putback_lru_page(page);
77 } else {
78 /*
79 * We lost the race. the page already moved to evictable list.
80 */
81 if (PageUnevictable(page))
82 count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
83 }
84}
85
86/*
87 * Mark page as mlocked if not already.
88 * If page on LRU, isolate and putback to move to unevictable list.
89 */
90void mlock_vma_page(struct page *page)
91{
92 /* Serialize with page migration */
93 BUG_ON(!PageLocked(page));
94
95 VM_BUG_ON_PAGE(PageTail(page), page);
96 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
97
98 if (!TestSetPageMlocked(page)) {
99 int nr_pages = thp_nr_pages(page);
100
101 mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
102 count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
103 if (!isolate_lru_page(page))
104 putback_lru_page(page);
105 }
106}
107
108/*
109 * Isolate a page from LRU with optional get_page() pin.
110 * Assumes lru_lock already held and page already pinned.
111 */
112static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
113{
114 if (PageLRU(page)) {
115 struct lruvec *lruvec;
116
117 lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
118 if (getpage)
119 get_page(page);
120 ClearPageLRU(page);
121 del_page_from_lru_list(page, lruvec, page_lru(page));
122 return true;
123 }
124
125 return false;
126}
127
128/*
129 * Finish munlock after successful page isolation
130 *
131 * Page must be locked. This is a wrapper for try_to_munlock()
132 * and putback_lru_page() with munlock accounting.
133 */
134static void __munlock_isolated_page(struct page *page)
135{
136 /*
137 * Optimization: if the page was mapped just once, that's our mapping
138 * and we don't need to check all the other vmas.
139 */
140 if (page_mapcount(page) > 1)
141 try_to_munlock(page);
142
143 /* Did try_to_unlock() succeed or punt? */
144 if (!PageMlocked(page))
145 count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page));
146
147 putback_lru_page(page);
148}
149
150/*
151 * Accounting for page isolation fail during munlock
152 *
153 * Performs accounting when page isolation fails in munlock. There is nothing
154 * else to do because it means some other task has already removed the page
155 * from the LRU. putback_lru_page() will take care of removing the page from
156 * the unevictable list, if necessary. vmscan [page_referenced()] will move
157 * the page back to the unevictable list if some other vma has it mlocked.
158 */
159static void __munlock_isolation_failed(struct page *page)
160{
161 int nr_pages = thp_nr_pages(page);
162
163 if (PageUnevictable(page))
164 __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
165 else
166 __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
167}
168
169/**
170 * munlock_vma_page - munlock a vma page
171 * @page: page to be unlocked, either a normal page or THP page head
172 *
173 * returns the size of the page as a page mask (0 for normal page,
174 * HPAGE_PMD_NR - 1 for THP head page)
175 *
176 * called from munlock()/munmap() path with page supposedly on the LRU.
177 * When we munlock a page, because the vma where we found the page is being
178 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
179 * page locked so that we can leave it on the unevictable lru list and not
180 * bother vmscan with it. However, to walk the page's rmap list in
181 * try_to_munlock() we must isolate the page from the LRU. If some other
182 * task has removed the page from the LRU, we won't be able to do that.
183 * So we clear the PageMlocked as we might not get another chance. If we
184 * can't isolate the page, we leave it for putback_lru_page() and vmscan
185 * [page_referenced()/try_to_unmap()] to deal with.
186 */
187unsigned int munlock_vma_page(struct page *page)
188{
189 int nr_pages;
190 pg_data_t *pgdat = page_pgdat(page);
191
192 /* For try_to_munlock() and to serialize with page migration */
193 BUG_ON(!PageLocked(page));
194
195 VM_BUG_ON_PAGE(PageTail(page), page);
196
197 /*
198 * Serialize with any parallel __split_huge_page_refcount() which
199 * might otherwise copy PageMlocked to part of the tail pages before
200 * we clear it in the head page. It also stabilizes thp_nr_pages().
201 */
202 spin_lock_irq(&pgdat->lru_lock);
203
204 if (!TestClearPageMlocked(page)) {
205 /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
206 nr_pages = 1;
207 goto unlock_out;
208 }
209
210 nr_pages = thp_nr_pages(page);
211 __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
212
213 if (__munlock_isolate_lru_page(page, true)) {
214 spin_unlock_irq(&pgdat->lru_lock);
215 __munlock_isolated_page(page);
216 goto out;
217 }
218 __munlock_isolation_failed(page);
219
220unlock_out:
221 spin_unlock_irq(&pgdat->lru_lock);
222
223out:
224 return nr_pages - 1;
225}
226
227/*
228 * convert get_user_pages() return value to posix mlock() error
229 */
230static int __mlock_posix_error_return(long retval)
231{
232 if (retval == -EFAULT)
233 retval = -ENOMEM;
234 else if (retval == -ENOMEM)
235 retval = -EAGAIN;
236 return retval;
237}
238
239/*
240 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
241 *
242 * The fast path is available only for evictable pages with single mapping.
243 * Then we can bypass the per-cpu pvec and get better performance.
244 * when mapcount > 1 we need try_to_munlock() which can fail.
245 * when !page_evictable(), we need the full redo logic of putback_lru_page to
246 * avoid leaving evictable page in unevictable list.
247 *
248 * In case of success, @page is added to @pvec and @pgrescued is incremented
249 * in case that the page was previously unevictable. @page is also unlocked.
250 */
251static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
252 int *pgrescued)
253{
254 VM_BUG_ON_PAGE(PageLRU(page), page);
255 VM_BUG_ON_PAGE(!PageLocked(page), page);
256
257 if (page_mapcount(page) <= 1 && page_evictable(page)) {
258 pagevec_add(pvec, page);
259 if (TestClearPageUnevictable(page))
260 (*pgrescued)++;
261 unlock_page(page);
262 return true;
263 }
264
265 return false;
266}
267
268/*
269 * Putback multiple evictable pages to the LRU
270 *
271 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
272 * the pages might have meanwhile become unevictable but that is OK.
273 */
274static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
275{
276 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
277 /*
278 *__pagevec_lru_add() calls release_pages() so we don't call
279 * put_page() explicitly
280 */
281 __pagevec_lru_add(pvec);
282 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
283}
284
285/*
286 * Munlock a batch of pages from the same zone
287 *
288 * The work is split to two main phases. First phase clears the Mlocked flag
289 * and attempts to isolate the pages, all under a single zone lru lock.
290 * The second phase finishes the munlock only for pages where isolation
291 * succeeded.
292 *
293 * Note that the pagevec may be modified during the process.
294 */
295static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
296{
297 int i;
298 int nr = pagevec_count(pvec);
299 int delta_munlocked = -nr;
300 struct pagevec pvec_putback;
301 int pgrescued = 0;
302
303 pagevec_init(&pvec_putback);
304
305 /* Phase 1: page isolation */
306 spin_lock_irq(&zone->zone_pgdat->lru_lock);
307 for (i = 0; i < nr; i++) {
308 struct page *page = pvec->pages[i];
309
310 if (TestClearPageMlocked(page)) {
311 /*
312 * We already have pin from follow_page_mask()
313 * so we can spare the get_page() here.
314 */
315 if (__munlock_isolate_lru_page(page, false))
316 continue;
317 else
318 __munlock_isolation_failed(page);
319 } else {
320 delta_munlocked++;
321 }
322
323 /*
324 * We won't be munlocking this page in the next phase
325 * but we still need to release the follow_page_mask()
326 * pin. We cannot do it under lru_lock however. If it's
327 * the last pin, __page_cache_release() would deadlock.
328 */
329 pagevec_add(&pvec_putback, pvec->pages[i]);
330 pvec->pages[i] = NULL;
331 }
332 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
333 spin_unlock_irq(&zone->zone_pgdat->lru_lock);
334
335 /* Now we can release pins of pages that we are not munlocking */
336 pagevec_release(&pvec_putback);
337
338 /* Phase 2: page munlock */
339 for (i = 0; i < nr; i++) {
340 struct page *page = pvec->pages[i];
341
342 if (page) {
343 lock_page(page);
344 if (!__putback_lru_fast_prepare(page, &pvec_putback,
345 &pgrescued)) {
346 /*
347 * Slow path. We don't want to lose the last
348 * pin before unlock_page()
349 */
350 get_page(page); /* for putback_lru_page() */
351 __munlock_isolated_page(page);
352 unlock_page(page);
353 put_page(page); /* from follow_page_mask() */
354 }
355 }
356 }
357
358 /*
359 * Phase 3: page putback for pages that qualified for the fast path
360 * This will also call put_page() to return pin from follow_page_mask()
361 */
362 if (pagevec_count(&pvec_putback))
363 __putback_lru_fast(&pvec_putback, pgrescued);
364}
365
366/*
367 * Fill up pagevec for __munlock_pagevec using pte walk
368 *
369 * The function expects that the struct page corresponding to @start address is
370 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
371 *
372 * The rest of @pvec is filled by subsequent pages within the same pmd and same
373 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
374 * pages also get pinned.
375 *
376 * Returns the address of the next page that should be scanned. This equals
377 * @start + PAGE_SIZE when no page could be added by the pte walk.
378 */
379static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
380 struct vm_area_struct *vma, struct zone *zone,
381 unsigned long start, unsigned long end)
382{
383 pte_t *pte;
384 spinlock_t *ptl;
385
386 /*
387 * Initialize pte walk starting at the already pinned page where we
388 * are sure that there is a pte, as it was pinned under the same
389 * mmap_lock write op.
390 */
391 pte = get_locked_pte(vma->vm_mm, start, &ptl);
392 /* Make sure we do not cross the page table boundary */
393 end = pgd_addr_end(start, end);
394 end = p4d_addr_end(start, end);
395 end = pud_addr_end(start, end);
396 end = pmd_addr_end(start, end);
397
398 /* The page next to the pinned page is the first we will try to get */
399 start += PAGE_SIZE;
400 while (start < end) {
401 struct page *page = NULL;
402 pte++;
403 if (pte_present(*pte))
404 page = vm_normal_page(vma, start, *pte);
405 /*
406 * Break if page could not be obtained or the page's node+zone does not
407 * match
408 */
409 if (!page || page_zone(page) != zone)
410 break;
411
412 /*
413 * Do not use pagevec for PTE-mapped THP,
414 * munlock_vma_pages_range() will handle them.
415 */
416 if (PageTransCompound(page))
417 break;
418
419 get_page(page);
420 /*
421 * Increase the address that will be returned *before* the
422 * eventual break due to pvec becoming full by adding the page
423 */
424 start += PAGE_SIZE;
425 if (pagevec_add(pvec, page) == 0)
426 break;
427 }
428 pte_unmap_unlock(pte, ptl);
429 return start;
430}
431
432/*
433 * munlock_vma_pages_range() - munlock all pages in the vma range.'
434 * @vma - vma containing range to be munlock()ed.
435 * @start - start address in @vma of the range
436 * @end - end of range in @vma.
437 *
438 * For mremap(), munmap() and exit().
439 *
440 * Called with @vma VM_LOCKED.
441 *
442 * Returns with VM_LOCKED cleared. Callers must be prepared to
443 * deal with this.
444 *
445 * We don't save and restore VM_LOCKED here because pages are
446 * still on lru. In unmap path, pages might be scanned by reclaim
447 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
448 * free them. This will result in freeing mlocked pages.
449 */
450void munlock_vma_pages_range(struct vm_area_struct *vma,
451 unsigned long start, unsigned long end)
452{
453 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
454
455 while (start < end) {
456 struct page *page;
457 unsigned int page_mask = 0;
458 unsigned long page_increm;
459 struct pagevec pvec;
460 struct zone *zone;
461
462 pagevec_init(&pvec);
463 /*
464 * Although FOLL_DUMP is intended for get_dump_page(),
465 * it just so happens that its special treatment of the
466 * ZERO_PAGE (returning an error instead of doing get_page)
467 * suits munlock very well (and if somehow an abnormal page
468 * has sneaked into the range, we won't oops here: great).
469 */
470 page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
471
472 if (page && !IS_ERR(page)) {
473 if (PageTransTail(page)) {
474 VM_BUG_ON_PAGE(PageMlocked(page), page);
475 put_page(page); /* follow_page_mask() */
476 } else if (PageTransHuge(page)) {
477 lock_page(page);
478 /*
479 * Any THP page found by follow_page_mask() may
480 * have gotten split before reaching
481 * munlock_vma_page(), so we need to compute
482 * the page_mask here instead.
483 */
484 page_mask = munlock_vma_page(page);
485 unlock_page(page);
486 put_page(page); /* follow_page_mask() */
487 } else {
488 /*
489 * Non-huge pages are handled in batches via
490 * pagevec. The pin from follow_page_mask()
491 * prevents them from collapsing by THP.
492 */
493 pagevec_add(&pvec, page);
494 zone = page_zone(page);
495
496 /*
497 * Try to fill the rest of pagevec using fast
498 * pte walk. This will also update start to
499 * the next page to process. Then munlock the
500 * pagevec.
501 */
502 start = __munlock_pagevec_fill(&pvec, vma,
503 zone, start, end);
504 __munlock_pagevec(&pvec, zone);
505 goto next;
506 }
507 }
508 page_increm = 1 + page_mask;
509 start += page_increm * PAGE_SIZE;
510next:
511 cond_resched();
512 }
513}
514
515/*
516 * mlock_fixup - handle mlock[all]/munlock[all] requests.
517 *
518 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
519 * munlock is a no-op. However, for some special vmas, we go ahead and
520 * populate the ptes.
521 *
522 * For vmas that pass the filters, merge/split as appropriate.
523 */
524static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
525 unsigned long start, unsigned long end, vm_flags_t newflags)
526{
527 struct mm_struct *mm = vma->vm_mm;
528 pgoff_t pgoff;
529 int nr_pages;
530 int ret = 0;
531 int lock = !!(newflags & VM_LOCKED);
532 vm_flags_t old_flags = vma->vm_flags;
533
534 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
535 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
536 vma_is_dax(vma))
537 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
538 goto out;
539
540 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
541 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
542 vma->vm_file, pgoff, vma_policy(vma),
543 vma->vm_userfaultfd_ctx);
544 if (*prev) {
545 vma = *prev;
546 goto success;
547 }
548
549 if (start != vma->vm_start) {
550 ret = split_vma(mm, vma, start, 1);
551 if (ret)
552 goto out;
553 }
554
555 if (end != vma->vm_end) {
556 ret = split_vma(mm, vma, end, 0);
557 if (ret)
558 goto out;
559 }
560
561success:
562 /*
563 * Keep track of amount of locked VM.
564 */
565 nr_pages = (end - start) >> PAGE_SHIFT;
566 if (!lock)
567 nr_pages = -nr_pages;
568 else if (old_flags & VM_LOCKED)
569 nr_pages = 0;
570 mm->locked_vm += nr_pages;
571
572 /*
573 * vm_flags is protected by the mmap_lock held in write mode.
574 * It's okay if try_to_unmap_one unmaps a page just after we
575 * set VM_LOCKED, populate_vma_page_range will bring it back.
576 */
577
578 if (lock)
579 vma->vm_flags = newflags;
580 else
581 munlock_vma_pages_range(vma, start, end);
582
583out:
584 *prev = vma;
585 return ret;
586}
587
588static int apply_vma_lock_flags(unsigned long start, size_t len,
589 vm_flags_t flags)
590{
591 unsigned long nstart, end, tmp;
592 struct vm_area_struct * vma, * prev;
593 int error;
594
595 VM_BUG_ON(offset_in_page(start));
596 VM_BUG_ON(len != PAGE_ALIGN(len));
597 end = start + len;
598 if (end < start)
599 return -EINVAL;
600 if (end == start)
601 return 0;
602 vma = find_vma(current->mm, start);
603 if (!vma || vma->vm_start > start)
604 return -ENOMEM;
605
606 prev = vma->vm_prev;
607 if (start > vma->vm_start)
608 prev = vma;
609
610 for (nstart = start ; ; ) {
611 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
612
613 newflags |= flags;
614
615 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
616 tmp = vma->vm_end;
617 if (tmp > end)
618 tmp = end;
619 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
620 if (error)
621 break;
622 nstart = tmp;
623 if (nstart < prev->vm_end)
624 nstart = prev->vm_end;
625 if (nstart >= end)
626 break;
627
628 vma = prev->vm_next;
629 if (!vma || vma->vm_start != nstart) {
630 error = -ENOMEM;
631 break;
632 }
633 }
634 return error;
635}
636
637/*
638 * Go through vma areas and sum size of mlocked
639 * vma pages, as return value.
640 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
641 * is also counted.
642 * Return value: previously mlocked page counts
643 */
644static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
645 unsigned long start, size_t len)
646{
647 struct vm_area_struct *vma;
648 unsigned long count = 0;
649
650 if (mm == NULL)
651 mm = current->mm;
652
653 vma = find_vma(mm, start);
654 if (vma == NULL)
655 vma = mm->mmap;
656
657 for (; vma ; vma = vma->vm_next) {
658 if (start >= vma->vm_end)
659 continue;
660 if (start + len <= vma->vm_start)
661 break;
662 if (vma->vm_flags & VM_LOCKED) {
663 if (start > vma->vm_start)
664 count -= (start - vma->vm_start);
665 if (start + len < vma->vm_end) {
666 count += start + len - vma->vm_start;
667 break;
668 }
669 count += vma->vm_end - vma->vm_start;
670 }
671 }
672
673 return count >> PAGE_SHIFT;
674}
675
676static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
677{
678 unsigned long locked;
679 unsigned long lock_limit;
680 int error = -ENOMEM;
681
682 start = untagged_addr(start);
683
684 if (!can_do_mlock())
685 return -EPERM;
686
687 len = PAGE_ALIGN(len + (offset_in_page(start)));
688 start &= PAGE_MASK;
689
690 lock_limit = rlimit(RLIMIT_MEMLOCK);
691 lock_limit >>= PAGE_SHIFT;
692 locked = len >> PAGE_SHIFT;
693
694 if (mmap_write_lock_killable(current->mm))
695 return -EINTR;
696
697 locked += current->mm->locked_vm;
698 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
699 /*
700 * It is possible that the regions requested intersect with
701 * previously mlocked areas, that part area in "mm->locked_vm"
702 * should not be counted to new mlock increment count. So check
703 * and adjust locked count if necessary.
704 */
705 locked -= count_mm_mlocked_page_nr(current->mm,
706 start, len);
707 }
708
709 /* check against resource limits */
710 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
711 error = apply_vma_lock_flags(start, len, flags);
712
713 mmap_write_unlock(current->mm);
714 if (error)
715 return error;
716
717 error = __mm_populate(start, len, 0);
718 if (error)
719 return __mlock_posix_error_return(error);
720 return 0;
721}
722
723SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
724{
725 return do_mlock(start, len, VM_LOCKED);
726}
727
728SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
729{
730 vm_flags_t vm_flags = VM_LOCKED;
731
732 if (flags & ~MLOCK_ONFAULT)
733 return -EINVAL;
734
735 if (flags & MLOCK_ONFAULT)
736 vm_flags |= VM_LOCKONFAULT;
737
738 return do_mlock(start, len, vm_flags);
739}
740
741SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
742{
743 int ret;
744
745 start = untagged_addr(start);
746
747 len = PAGE_ALIGN(len + (offset_in_page(start)));
748 start &= PAGE_MASK;
749
750 if (mmap_write_lock_killable(current->mm))
751 return -EINTR;
752 ret = apply_vma_lock_flags(start, len, 0);
753 mmap_write_unlock(current->mm);
754
755 return ret;
756}
757
758/*
759 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
760 * and translate into the appropriate modifications to mm->def_flags and/or the
761 * flags for all current VMAs.
762 *
763 * There are a couple of subtleties with this. If mlockall() is called multiple
764 * times with different flags, the values do not necessarily stack. If mlockall
765 * is called once including the MCL_FUTURE flag and then a second time without
766 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
767 */
768static int apply_mlockall_flags(int flags)
769{
770 struct vm_area_struct * vma, * prev = NULL;
771 vm_flags_t to_add = 0;
772
773 current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
774 if (flags & MCL_FUTURE) {
775 current->mm->def_flags |= VM_LOCKED;
776
777 if (flags & MCL_ONFAULT)
778 current->mm->def_flags |= VM_LOCKONFAULT;
779
780 if (!(flags & MCL_CURRENT))
781 goto out;
782 }
783
784 if (flags & MCL_CURRENT) {
785 to_add |= VM_LOCKED;
786 if (flags & MCL_ONFAULT)
787 to_add |= VM_LOCKONFAULT;
788 }
789
790 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
791 vm_flags_t newflags;
792
793 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
794 newflags |= to_add;
795
796 /* Ignore errors */
797 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
798 cond_resched();
799 }
800out:
801 return 0;
802}
803
804SYSCALL_DEFINE1(mlockall, int, flags)
805{
806 unsigned long lock_limit;
807 int ret;
808
809 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
810 flags == MCL_ONFAULT)
811 return -EINVAL;
812
813 if (!can_do_mlock())
814 return -EPERM;
815
816 lock_limit = rlimit(RLIMIT_MEMLOCK);
817 lock_limit >>= PAGE_SHIFT;
818
819 if (mmap_write_lock_killable(current->mm))
820 return -EINTR;
821
822 ret = -ENOMEM;
823 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
824 capable(CAP_IPC_LOCK))
825 ret = apply_mlockall_flags(flags);
826 mmap_write_unlock(current->mm);
827 if (!ret && (flags & MCL_CURRENT))
828 mm_populate(0, TASK_SIZE);
829
830 return ret;
831}
832
833SYSCALL_DEFINE0(munlockall)
834{
835 int ret;
836
837 if (mmap_write_lock_killable(current->mm))
838 return -EINTR;
839 ret = apply_mlockall_flags(0);
840 mmap_write_unlock(current->mm);
841 return ret;
842}
843
844/*
845 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
846 * shm segments) get accounted against the user_struct instead.
847 */
848static DEFINE_SPINLOCK(shmlock_user_lock);
849
850int user_shm_lock(size_t size, struct user_struct *user)
851{
852 unsigned long lock_limit, locked;
853 int allowed = 0;
854
855 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
856 lock_limit = rlimit(RLIMIT_MEMLOCK);
857 if (lock_limit == RLIM_INFINITY)
858 allowed = 1;
859 lock_limit >>= PAGE_SHIFT;
860 spin_lock(&shmlock_user_lock);
861 if (!allowed &&
862 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
863 goto out;
864 get_uid(user);
865 user->locked_shm += locked;
866 allowed = 1;
867out:
868 spin_unlock(&shmlock_user_lock);
869 return allowed;
870}
871
872void user_shm_unlock(size_t size, struct user_struct *user)
873{
874 spin_lock(&shmlock_user_lock);
875 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
876 spin_unlock(&shmlock_user_lock);
877 free_uid(user);
878}
1/*
2 * linux/mm/mlock.c
3 *
4 * (C) Copyright 1995 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
6 */
7
8#include <linux/capability.h>
9#include <linux/mman.h>
10#include <linux/mm.h>
11#include <linux/swap.h>
12#include <linux/swapops.h>
13#include <linux/pagemap.h>
14#include <linux/pagevec.h>
15#include <linux/mempolicy.h>
16#include <linux/syscalls.h>
17#include <linux/sched.h>
18#include <linux/export.h>
19#include <linux/rmap.h>
20#include <linux/mmzone.h>
21#include <linux/hugetlb.h>
22#include <linux/memcontrol.h>
23#include <linux/mm_inline.h>
24
25#include "internal.h"
26
27bool can_do_mlock(void)
28{
29 if (rlimit(RLIMIT_MEMLOCK) != 0)
30 return true;
31 if (capable(CAP_IPC_LOCK))
32 return true;
33 return false;
34}
35EXPORT_SYMBOL(can_do_mlock);
36
37/*
38 * Mlocked pages are marked with PageMlocked() flag for efficient testing
39 * in vmscan and, possibly, the fault path; and to support semi-accurate
40 * statistics.
41 *
42 * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
43 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
44 * The unevictable list is an LRU sibling list to the [in]active lists.
45 * PageUnevictable is set to indicate the unevictable state.
46 *
47 * When lazy mlocking via vmscan, it is important to ensure that the
48 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
49 * may have mlocked a page that is being munlocked. So lazy mlock must take
50 * the mmap_sem for read, and verify that the vma really is locked
51 * (see mm/rmap.c).
52 */
53
54/*
55 * LRU accounting for clear_page_mlock()
56 */
57void clear_page_mlock(struct page *page)
58{
59 if (!TestClearPageMlocked(page))
60 return;
61
62 mod_zone_page_state(page_zone(page), NR_MLOCK,
63 -hpage_nr_pages(page));
64 count_vm_event(UNEVICTABLE_PGCLEARED);
65 if (!isolate_lru_page(page)) {
66 putback_lru_page(page);
67 } else {
68 /*
69 * We lost the race. the page already moved to evictable list.
70 */
71 if (PageUnevictable(page))
72 count_vm_event(UNEVICTABLE_PGSTRANDED);
73 }
74}
75
76/*
77 * Mark page as mlocked if not already.
78 * If page on LRU, isolate and putback to move to unevictable list.
79 */
80void mlock_vma_page(struct page *page)
81{
82 /* Serialize with page migration */
83 BUG_ON(!PageLocked(page));
84
85 VM_BUG_ON_PAGE(PageTail(page), page);
86 VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
87
88 if (!TestSetPageMlocked(page)) {
89 mod_zone_page_state(page_zone(page), NR_MLOCK,
90 hpage_nr_pages(page));
91 count_vm_event(UNEVICTABLE_PGMLOCKED);
92 if (!isolate_lru_page(page))
93 putback_lru_page(page);
94 }
95}
96
97/*
98 * Isolate a page from LRU with optional get_page() pin.
99 * Assumes lru_lock already held and page already pinned.
100 */
101static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
102{
103 if (PageLRU(page)) {
104 struct lruvec *lruvec;
105
106 lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
107 if (getpage)
108 get_page(page);
109 ClearPageLRU(page);
110 del_page_from_lru_list(page, lruvec, page_lru(page));
111 return true;
112 }
113
114 return false;
115}
116
117/*
118 * Finish munlock after successful page isolation
119 *
120 * Page must be locked. This is a wrapper for try_to_munlock()
121 * and putback_lru_page() with munlock accounting.
122 */
123static void __munlock_isolated_page(struct page *page)
124{
125 int ret = SWAP_AGAIN;
126
127 /*
128 * Optimization: if the page was mapped just once, that's our mapping
129 * and we don't need to check all the other vmas.
130 */
131 if (page_mapcount(page) > 1)
132 ret = try_to_munlock(page);
133
134 /* Did try_to_unlock() succeed or punt? */
135 if (ret != SWAP_MLOCK)
136 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
137
138 putback_lru_page(page);
139}
140
141/*
142 * Accounting for page isolation fail during munlock
143 *
144 * Performs accounting when page isolation fails in munlock. There is nothing
145 * else to do because it means some other task has already removed the page
146 * from the LRU. putback_lru_page() will take care of removing the page from
147 * the unevictable list, if necessary. vmscan [page_referenced()] will move
148 * the page back to the unevictable list if some other vma has it mlocked.
149 */
150static void __munlock_isolation_failed(struct page *page)
151{
152 if (PageUnevictable(page))
153 __count_vm_event(UNEVICTABLE_PGSTRANDED);
154 else
155 __count_vm_event(UNEVICTABLE_PGMUNLOCKED);
156}
157
158/**
159 * munlock_vma_page - munlock a vma page
160 * @page - page to be unlocked, either a normal page or THP page head
161 *
162 * returns the size of the page as a page mask (0 for normal page,
163 * HPAGE_PMD_NR - 1 for THP head page)
164 *
165 * called from munlock()/munmap() path with page supposedly on the LRU.
166 * When we munlock a page, because the vma where we found the page is being
167 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
168 * page locked so that we can leave it on the unevictable lru list and not
169 * bother vmscan with it. However, to walk the page's rmap list in
170 * try_to_munlock() we must isolate the page from the LRU. If some other
171 * task has removed the page from the LRU, we won't be able to do that.
172 * So we clear the PageMlocked as we might not get another chance. If we
173 * can't isolate the page, we leave it for putback_lru_page() and vmscan
174 * [page_referenced()/try_to_unmap()] to deal with.
175 */
176unsigned int munlock_vma_page(struct page *page)
177{
178 int nr_pages;
179 struct zone *zone = page_zone(page);
180
181 /* For try_to_munlock() and to serialize with page migration */
182 BUG_ON(!PageLocked(page));
183
184 VM_BUG_ON_PAGE(PageTail(page), page);
185
186 /*
187 * Serialize with any parallel __split_huge_page_refcount() which
188 * might otherwise copy PageMlocked to part of the tail pages before
189 * we clear it in the head page. It also stabilizes hpage_nr_pages().
190 */
191 spin_lock_irq(zone_lru_lock(zone));
192
193 if (!TestClearPageMlocked(page)) {
194 /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
195 nr_pages = 1;
196 goto unlock_out;
197 }
198
199 nr_pages = hpage_nr_pages(page);
200 __mod_zone_page_state(zone, NR_MLOCK, -nr_pages);
201
202 if (__munlock_isolate_lru_page(page, true)) {
203 spin_unlock_irq(zone_lru_lock(zone));
204 __munlock_isolated_page(page);
205 goto out;
206 }
207 __munlock_isolation_failed(page);
208
209unlock_out:
210 spin_unlock_irq(zone_lru_lock(zone));
211
212out:
213 return nr_pages - 1;
214}
215
216/*
217 * convert get_user_pages() return value to posix mlock() error
218 */
219static int __mlock_posix_error_return(long retval)
220{
221 if (retval == -EFAULT)
222 retval = -ENOMEM;
223 else if (retval == -ENOMEM)
224 retval = -EAGAIN;
225 return retval;
226}
227
228/*
229 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
230 *
231 * The fast path is available only for evictable pages with single mapping.
232 * Then we can bypass the per-cpu pvec and get better performance.
233 * when mapcount > 1 we need try_to_munlock() which can fail.
234 * when !page_evictable(), we need the full redo logic of putback_lru_page to
235 * avoid leaving evictable page in unevictable list.
236 *
237 * In case of success, @page is added to @pvec and @pgrescued is incremented
238 * in case that the page was previously unevictable. @page is also unlocked.
239 */
240static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
241 int *pgrescued)
242{
243 VM_BUG_ON_PAGE(PageLRU(page), page);
244 VM_BUG_ON_PAGE(!PageLocked(page), page);
245
246 if (page_mapcount(page) <= 1 && page_evictable(page)) {
247 pagevec_add(pvec, page);
248 if (TestClearPageUnevictable(page))
249 (*pgrescued)++;
250 unlock_page(page);
251 return true;
252 }
253
254 return false;
255}
256
257/*
258 * Putback multiple evictable pages to the LRU
259 *
260 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
261 * the pages might have meanwhile become unevictable but that is OK.
262 */
263static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
264{
265 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
266 /*
267 *__pagevec_lru_add() calls release_pages() so we don't call
268 * put_page() explicitly
269 */
270 __pagevec_lru_add(pvec);
271 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
272}
273
274/*
275 * Munlock a batch of pages from the same zone
276 *
277 * The work is split to two main phases. First phase clears the Mlocked flag
278 * and attempts to isolate the pages, all under a single zone lru lock.
279 * The second phase finishes the munlock only for pages where isolation
280 * succeeded.
281 *
282 * Note that the pagevec may be modified during the process.
283 */
284static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
285{
286 int i;
287 int nr = pagevec_count(pvec);
288 int delta_munlocked;
289 struct pagevec pvec_putback;
290 int pgrescued = 0;
291
292 pagevec_init(&pvec_putback, 0);
293
294 /* Phase 1: page isolation */
295 spin_lock_irq(zone_lru_lock(zone));
296 for (i = 0; i < nr; i++) {
297 struct page *page = pvec->pages[i];
298
299 if (TestClearPageMlocked(page)) {
300 /*
301 * We already have pin from follow_page_mask()
302 * so we can spare the get_page() here.
303 */
304 if (__munlock_isolate_lru_page(page, false))
305 continue;
306 else
307 __munlock_isolation_failed(page);
308 }
309
310 /*
311 * We won't be munlocking this page in the next phase
312 * but we still need to release the follow_page_mask()
313 * pin. We cannot do it under lru_lock however. If it's
314 * the last pin, __page_cache_release() would deadlock.
315 */
316 pagevec_add(&pvec_putback, pvec->pages[i]);
317 pvec->pages[i] = NULL;
318 }
319 delta_munlocked = -nr + pagevec_count(&pvec_putback);
320 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
321 spin_unlock_irq(zone_lru_lock(zone));
322
323 /* Now we can release pins of pages that we are not munlocking */
324 pagevec_release(&pvec_putback);
325
326 /* Phase 2: page munlock */
327 for (i = 0; i < nr; i++) {
328 struct page *page = pvec->pages[i];
329
330 if (page) {
331 lock_page(page);
332 if (!__putback_lru_fast_prepare(page, &pvec_putback,
333 &pgrescued)) {
334 /*
335 * Slow path. We don't want to lose the last
336 * pin before unlock_page()
337 */
338 get_page(page); /* for putback_lru_page() */
339 __munlock_isolated_page(page);
340 unlock_page(page);
341 put_page(page); /* from follow_page_mask() */
342 }
343 }
344 }
345
346 /*
347 * Phase 3: page putback for pages that qualified for the fast path
348 * This will also call put_page() to return pin from follow_page_mask()
349 */
350 if (pagevec_count(&pvec_putback))
351 __putback_lru_fast(&pvec_putback, pgrescued);
352}
353
354/*
355 * Fill up pagevec for __munlock_pagevec using pte walk
356 *
357 * The function expects that the struct page corresponding to @start address is
358 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
359 *
360 * The rest of @pvec is filled by subsequent pages within the same pmd and same
361 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
362 * pages also get pinned.
363 *
364 * Returns the address of the next page that should be scanned. This equals
365 * @start + PAGE_SIZE when no page could be added by the pte walk.
366 */
367static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
368 struct vm_area_struct *vma, int zoneid, unsigned long start,
369 unsigned long end)
370{
371 pte_t *pte;
372 spinlock_t *ptl;
373
374 /*
375 * Initialize pte walk starting at the already pinned page where we
376 * are sure that there is a pte, as it was pinned under the same
377 * mmap_sem write op.
378 */
379 pte = get_locked_pte(vma->vm_mm, start, &ptl);
380 /* Make sure we do not cross the page table boundary */
381 end = pgd_addr_end(start, end);
382 end = pud_addr_end(start, end);
383 end = pmd_addr_end(start, end);
384
385 /* The page next to the pinned page is the first we will try to get */
386 start += PAGE_SIZE;
387 while (start < end) {
388 struct page *page = NULL;
389 pte++;
390 if (pte_present(*pte))
391 page = vm_normal_page(vma, start, *pte);
392 /*
393 * Break if page could not be obtained or the page's node+zone does not
394 * match
395 */
396 if (!page || page_zone_id(page) != zoneid)
397 break;
398
399 /*
400 * Do not use pagevec for PTE-mapped THP,
401 * munlock_vma_pages_range() will handle them.
402 */
403 if (PageTransCompound(page))
404 break;
405
406 get_page(page);
407 /*
408 * Increase the address that will be returned *before* the
409 * eventual break due to pvec becoming full by adding the page
410 */
411 start += PAGE_SIZE;
412 if (pagevec_add(pvec, page) == 0)
413 break;
414 }
415 pte_unmap_unlock(pte, ptl);
416 return start;
417}
418
419/*
420 * munlock_vma_pages_range() - munlock all pages in the vma range.'
421 * @vma - vma containing range to be munlock()ed.
422 * @start - start address in @vma of the range
423 * @end - end of range in @vma.
424 *
425 * For mremap(), munmap() and exit().
426 *
427 * Called with @vma VM_LOCKED.
428 *
429 * Returns with VM_LOCKED cleared. Callers must be prepared to
430 * deal with this.
431 *
432 * We don't save and restore VM_LOCKED here because pages are
433 * still on lru. In unmap path, pages might be scanned by reclaim
434 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
435 * free them. This will result in freeing mlocked pages.
436 */
437void munlock_vma_pages_range(struct vm_area_struct *vma,
438 unsigned long start, unsigned long end)
439{
440 vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
441
442 while (start < end) {
443 struct page *page;
444 unsigned int page_mask = 0;
445 unsigned long page_increm;
446 struct pagevec pvec;
447 struct zone *zone;
448 int zoneid;
449
450 pagevec_init(&pvec, 0);
451 /*
452 * Although FOLL_DUMP is intended for get_dump_page(),
453 * it just so happens that its special treatment of the
454 * ZERO_PAGE (returning an error instead of doing get_page)
455 * suits munlock very well (and if somehow an abnormal page
456 * has sneaked into the range, we won't oops here: great).
457 */
458 page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
459
460 if (page && !IS_ERR(page)) {
461 if (PageTransTail(page)) {
462 VM_BUG_ON_PAGE(PageMlocked(page), page);
463 put_page(page); /* follow_page_mask() */
464 } else if (PageTransHuge(page)) {
465 lock_page(page);
466 /*
467 * Any THP page found by follow_page_mask() may
468 * have gotten split before reaching
469 * munlock_vma_page(), so we need to compute
470 * the page_mask here instead.
471 */
472 page_mask = munlock_vma_page(page);
473 unlock_page(page);
474 put_page(page); /* follow_page_mask() */
475 } else {
476 /*
477 * Non-huge pages are handled in batches via
478 * pagevec. The pin from follow_page_mask()
479 * prevents them from collapsing by THP.
480 */
481 pagevec_add(&pvec, page);
482 zone = page_zone(page);
483 zoneid = page_zone_id(page);
484
485 /*
486 * Try to fill the rest of pagevec using fast
487 * pte walk. This will also update start to
488 * the next page to process. Then munlock the
489 * pagevec.
490 */
491 start = __munlock_pagevec_fill(&pvec, vma,
492 zoneid, start, end);
493 __munlock_pagevec(&pvec, zone);
494 goto next;
495 }
496 }
497 page_increm = 1 + page_mask;
498 start += page_increm * PAGE_SIZE;
499next:
500 cond_resched();
501 }
502}
503
504/*
505 * mlock_fixup - handle mlock[all]/munlock[all] requests.
506 *
507 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
508 * munlock is a no-op. However, for some special vmas, we go ahead and
509 * populate the ptes.
510 *
511 * For vmas that pass the filters, merge/split as appropriate.
512 */
513static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
514 unsigned long start, unsigned long end, vm_flags_t newflags)
515{
516 struct mm_struct *mm = vma->vm_mm;
517 pgoff_t pgoff;
518 int nr_pages;
519 int ret = 0;
520 int lock = !!(newflags & VM_LOCKED);
521 vm_flags_t old_flags = vma->vm_flags;
522
523 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
524 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
525 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
526 goto out;
527
528 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
529 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
530 vma->vm_file, pgoff, vma_policy(vma),
531 vma->vm_userfaultfd_ctx);
532 if (*prev) {
533 vma = *prev;
534 goto success;
535 }
536
537 if (start != vma->vm_start) {
538 ret = split_vma(mm, vma, start, 1);
539 if (ret)
540 goto out;
541 }
542
543 if (end != vma->vm_end) {
544 ret = split_vma(mm, vma, end, 0);
545 if (ret)
546 goto out;
547 }
548
549success:
550 /*
551 * Keep track of amount of locked VM.
552 */
553 nr_pages = (end - start) >> PAGE_SHIFT;
554 if (!lock)
555 nr_pages = -nr_pages;
556 else if (old_flags & VM_LOCKED)
557 nr_pages = 0;
558 mm->locked_vm += nr_pages;
559
560 /*
561 * vm_flags is protected by the mmap_sem held in write mode.
562 * It's okay if try_to_unmap_one unmaps a page just after we
563 * set VM_LOCKED, populate_vma_page_range will bring it back.
564 */
565
566 if (lock)
567 vma->vm_flags = newflags;
568 else
569 munlock_vma_pages_range(vma, start, end);
570
571out:
572 *prev = vma;
573 return ret;
574}
575
576static int apply_vma_lock_flags(unsigned long start, size_t len,
577 vm_flags_t flags)
578{
579 unsigned long nstart, end, tmp;
580 struct vm_area_struct * vma, * prev;
581 int error;
582
583 VM_BUG_ON(offset_in_page(start));
584 VM_BUG_ON(len != PAGE_ALIGN(len));
585 end = start + len;
586 if (end < start)
587 return -EINVAL;
588 if (end == start)
589 return 0;
590 vma = find_vma(current->mm, start);
591 if (!vma || vma->vm_start > start)
592 return -ENOMEM;
593
594 prev = vma->vm_prev;
595 if (start > vma->vm_start)
596 prev = vma;
597
598 for (nstart = start ; ; ) {
599 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
600
601 newflags |= flags;
602
603 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
604 tmp = vma->vm_end;
605 if (tmp > end)
606 tmp = end;
607 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
608 if (error)
609 break;
610 nstart = tmp;
611 if (nstart < prev->vm_end)
612 nstart = prev->vm_end;
613 if (nstart >= end)
614 break;
615
616 vma = prev->vm_next;
617 if (!vma || vma->vm_start != nstart) {
618 error = -ENOMEM;
619 break;
620 }
621 }
622 return error;
623}
624
625/*
626 * Go through vma areas and sum size of mlocked
627 * vma pages, as return value.
628 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
629 * is also counted.
630 * Return value: previously mlocked page counts
631 */
632static int count_mm_mlocked_page_nr(struct mm_struct *mm,
633 unsigned long start, size_t len)
634{
635 struct vm_area_struct *vma;
636 int count = 0;
637
638 if (mm == NULL)
639 mm = current->mm;
640
641 vma = find_vma(mm, start);
642 if (vma == NULL)
643 vma = mm->mmap;
644
645 for (; vma ; vma = vma->vm_next) {
646 if (start >= vma->vm_end)
647 continue;
648 if (start + len <= vma->vm_start)
649 break;
650 if (vma->vm_flags & VM_LOCKED) {
651 if (start > vma->vm_start)
652 count -= (start - vma->vm_start);
653 if (start + len < vma->vm_end) {
654 count += start + len - vma->vm_start;
655 break;
656 }
657 count += vma->vm_end - vma->vm_start;
658 }
659 }
660
661 return count >> PAGE_SHIFT;
662}
663
664static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
665{
666 unsigned long locked;
667 unsigned long lock_limit;
668 int error = -ENOMEM;
669
670 if (!can_do_mlock())
671 return -EPERM;
672
673 lru_add_drain_all(); /* flush pagevec */
674
675 len = PAGE_ALIGN(len + (offset_in_page(start)));
676 start &= PAGE_MASK;
677
678 lock_limit = rlimit(RLIMIT_MEMLOCK);
679 lock_limit >>= PAGE_SHIFT;
680 locked = len >> PAGE_SHIFT;
681
682 if (down_write_killable(¤t->mm->mmap_sem))
683 return -EINTR;
684
685 locked += current->mm->locked_vm;
686 if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
687 /*
688 * It is possible that the regions requested intersect with
689 * previously mlocked areas, that part area in "mm->locked_vm"
690 * should not be counted to new mlock increment count. So check
691 * and adjust locked count if necessary.
692 */
693 locked -= count_mm_mlocked_page_nr(current->mm,
694 start, len);
695 }
696
697 /* check against resource limits */
698 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
699 error = apply_vma_lock_flags(start, len, flags);
700
701 up_write(¤t->mm->mmap_sem);
702 if (error)
703 return error;
704
705 error = __mm_populate(start, len, 0);
706 if (error)
707 return __mlock_posix_error_return(error);
708 return 0;
709}
710
711SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
712{
713 return do_mlock(start, len, VM_LOCKED);
714}
715
716SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
717{
718 vm_flags_t vm_flags = VM_LOCKED;
719
720 if (flags & ~MLOCK_ONFAULT)
721 return -EINVAL;
722
723 if (flags & MLOCK_ONFAULT)
724 vm_flags |= VM_LOCKONFAULT;
725
726 return do_mlock(start, len, vm_flags);
727}
728
729SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
730{
731 int ret;
732
733 len = PAGE_ALIGN(len + (offset_in_page(start)));
734 start &= PAGE_MASK;
735
736 if (down_write_killable(¤t->mm->mmap_sem))
737 return -EINTR;
738 ret = apply_vma_lock_flags(start, len, 0);
739 up_write(¤t->mm->mmap_sem);
740
741 return ret;
742}
743
744/*
745 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
746 * and translate into the appropriate modifications to mm->def_flags and/or the
747 * flags for all current VMAs.
748 *
749 * There are a couple of subtleties with this. If mlockall() is called multiple
750 * times with different flags, the values do not necessarily stack. If mlockall
751 * is called once including the MCL_FUTURE flag and then a second time without
752 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
753 */
754static int apply_mlockall_flags(int flags)
755{
756 struct vm_area_struct * vma, * prev = NULL;
757 vm_flags_t to_add = 0;
758
759 current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
760 if (flags & MCL_FUTURE) {
761 current->mm->def_flags |= VM_LOCKED;
762
763 if (flags & MCL_ONFAULT)
764 current->mm->def_flags |= VM_LOCKONFAULT;
765
766 if (!(flags & MCL_CURRENT))
767 goto out;
768 }
769
770 if (flags & MCL_CURRENT) {
771 to_add |= VM_LOCKED;
772 if (flags & MCL_ONFAULT)
773 to_add |= VM_LOCKONFAULT;
774 }
775
776 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
777 vm_flags_t newflags;
778
779 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
780 newflags |= to_add;
781
782 /* Ignore errors */
783 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
784 cond_resched_rcu_qs();
785 }
786out:
787 return 0;
788}
789
790SYSCALL_DEFINE1(mlockall, int, flags)
791{
792 unsigned long lock_limit;
793 int ret;
794
795 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
796 return -EINVAL;
797
798 if (!can_do_mlock())
799 return -EPERM;
800
801 if (flags & MCL_CURRENT)
802 lru_add_drain_all(); /* flush pagevec */
803
804 lock_limit = rlimit(RLIMIT_MEMLOCK);
805 lock_limit >>= PAGE_SHIFT;
806
807 if (down_write_killable(¤t->mm->mmap_sem))
808 return -EINTR;
809
810 ret = -ENOMEM;
811 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
812 capable(CAP_IPC_LOCK))
813 ret = apply_mlockall_flags(flags);
814 up_write(¤t->mm->mmap_sem);
815 if (!ret && (flags & MCL_CURRENT))
816 mm_populate(0, TASK_SIZE);
817
818 return ret;
819}
820
821SYSCALL_DEFINE0(munlockall)
822{
823 int ret;
824
825 if (down_write_killable(¤t->mm->mmap_sem))
826 return -EINTR;
827 ret = apply_mlockall_flags(0);
828 up_write(¤t->mm->mmap_sem);
829 return ret;
830}
831
832/*
833 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
834 * shm segments) get accounted against the user_struct instead.
835 */
836static DEFINE_SPINLOCK(shmlock_user_lock);
837
838int user_shm_lock(size_t size, struct user_struct *user)
839{
840 unsigned long lock_limit, locked;
841 int allowed = 0;
842
843 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
844 lock_limit = rlimit(RLIMIT_MEMLOCK);
845 if (lock_limit == RLIM_INFINITY)
846 allowed = 1;
847 lock_limit >>= PAGE_SHIFT;
848 spin_lock(&shmlock_user_lock);
849 if (!allowed &&
850 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
851 goto out;
852 get_uid(user);
853 user->locked_shm += locked;
854 allowed = 1;
855out:
856 spin_unlock(&shmlock_user_lock);
857 return allowed;
858}
859
860void user_shm_unlock(size_t size, struct user_struct *user)
861{
862 spin_lock(&shmlock_user_lock);
863 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
864 spin_unlock(&shmlock_user_lock);
865 free_uid(user);
866}