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Linux/mm/mlock.c

  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 
 27 bool 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 }
 35 EXPORT_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  */
 57 void 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  */
 80 void 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  */
101 static 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  */
123 static 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  */
150 static 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  */
176 unsigned 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 
209 unlock_out:
210         spin_unlock_irq(zone_lru_lock(zone));
211 
212 out:
213         return nr_pages - 1;
214 }
215 
216 /*
217  * convert get_user_pages() return value to posix mlock() error
218  */
219 static 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  */
240 static 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  */
263 static 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  */
284 static 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  */
367 static 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  */
437 void 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;
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_mask(vma, start, FOLL_GET | FOLL_DUMP,
459                                 &page_mask);
460 
461                 if (page && !IS_ERR(page)) {
462                         if (PageTransTail(page)) {
463                                 VM_BUG_ON_PAGE(PageMlocked(page), page);
464                                 put_page(page); /* follow_page_mask() */
465                         } else if (PageTransHuge(page)) {
466                                 lock_page(page);
467                                 /*
468                                  * Any THP page found by follow_page_mask() may
469                                  * have gotten split before reaching
470                                  * munlock_vma_page(), so we need to recompute
471                                  * the page_mask here.
472                                  */
473                                 page_mask = munlock_vma_page(page);
474                                 unlock_page(page);
475                                 put_page(page); /* follow_page_mask() */
476                         } else {
477                                 /*
478                                  * Non-huge pages are handled in batches via
479                                  * pagevec. The pin from follow_page_mask()
480                                  * prevents them from collapsing by THP.
481                                  */
482                                 pagevec_add(&pvec, page);
483                                 zone = page_zone(page);
484                                 zoneid = page_zone_id(page);
485 
486                                 /*
487                                  * Try to fill the rest of pagevec using fast
488                                  * pte walk. This will also update start to
489                                  * the next page to process. Then munlock the
490                                  * pagevec.
491                                  */
492                                 start = __munlock_pagevec_fill(&pvec, vma,
493                                                 zoneid, start, end);
494                                 __munlock_pagevec(&pvec, zone);
495                                 goto next;
496                         }
497                 }
498                 page_increm = 1 + page_mask;
499                 start += page_increm * PAGE_SIZE;
500 next:
501                 cond_resched();
502         }
503 }
504 
505 /*
506  * mlock_fixup  - handle mlock[all]/munlock[all] requests.
507  *
508  * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
509  * munlock is a no-op.  However, for some special vmas, we go ahead and
510  * populate the ptes.
511  *
512  * For vmas that pass the filters, merge/split as appropriate.
513  */
514 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
515         unsigned long start, unsigned long end, vm_flags_t newflags)
516 {
517         struct mm_struct *mm = vma->vm_mm;
518         pgoff_t pgoff;
519         int nr_pages;
520         int ret = 0;
521         int lock = !!(newflags & VM_LOCKED);
522         vm_flags_t old_flags = vma->vm_flags;
523 
524         if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
525             is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
526                 /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
527                 goto out;
528 
529         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
530         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
531                           vma->vm_file, pgoff, vma_policy(vma),
532                           vma->vm_userfaultfd_ctx);
533         if (*prev) {
534                 vma = *prev;
535                 goto success;
536         }
537 
538         if (start != vma->vm_start) {
539                 ret = split_vma(mm, vma, start, 1);
540                 if (ret)
541                         goto out;
542         }
543 
544         if (end != vma->vm_end) {
545                 ret = split_vma(mm, vma, end, 0);
546                 if (ret)
547                         goto out;
548         }
549 
550 success:
551         /*
552          * Keep track of amount of locked VM.
553          */
554         nr_pages = (end - start) >> PAGE_SHIFT;
555         if (!lock)
556                 nr_pages = -nr_pages;
557         else if (old_flags & VM_LOCKED)
558                 nr_pages = 0;
559         mm->locked_vm += nr_pages;
560 
561         /*
562          * vm_flags is protected by the mmap_sem held in write mode.
563          * It's okay if try_to_unmap_one unmaps a page just after we
564          * set VM_LOCKED, populate_vma_page_range will bring it back.
565          */
566 
567         if (lock)
568                 vma->vm_flags = newflags;
569         else
570                 munlock_vma_pages_range(vma, start, end);
571 
572 out:
573         *prev = vma;
574         return ret;
575 }
576 
577 static int apply_vma_lock_flags(unsigned long start, size_t len,
578                                 vm_flags_t flags)
579 {
580         unsigned long nstart, end, tmp;
581         struct vm_area_struct * vma, * prev;
582         int error;
583 
584         VM_BUG_ON(offset_in_page(start));
585         VM_BUG_ON(len != PAGE_ALIGN(len));
586         end = start + len;
587         if (end < start)
588                 return -EINVAL;
589         if (end == start)
590                 return 0;
591         vma = find_vma(current->mm, start);
592         if (!vma || vma->vm_start > start)
593                 return -ENOMEM;
594 
595         prev = vma->vm_prev;
596         if (start > vma->vm_start)
597                 prev = vma;
598 
599         for (nstart = start ; ; ) {
600                 vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
601 
602                 newflags |= flags;
603 
604                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
605                 tmp = vma->vm_end;
606                 if (tmp > end)
607                         tmp = end;
608                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
609                 if (error)
610                         break;
611                 nstart = tmp;
612                 if (nstart < prev->vm_end)
613                         nstart = prev->vm_end;
614                 if (nstart >= end)
615                         break;
616 
617                 vma = prev->vm_next;
618                 if (!vma || vma->vm_start != nstart) {
619                         error = -ENOMEM;
620                         break;
621                 }
622         }
623         return error;
624 }
625 
626 /*
627  * Go through vma areas and sum size of mlocked
628  * vma pages, as return value.
629  * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
630  * is also counted.
631  * Return value: previously mlocked page counts
632  */
633 static int count_mm_mlocked_page_nr(struct mm_struct *mm,
634                 unsigned long start, size_t len)
635 {
636         struct vm_area_struct *vma;
637         int count = 0;
638 
639         if (mm == NULL)
640                 mm = current->mm;
641 
642         vma = find_vma(mm, start);
643         if (vma == NULL)
644                 vma = mm->mmap;
645 
646         for (; vma ; vma = vma->vm_next) {
647                 if (start >= vma->vm_end)
648                         continue;
649                 if (start + len <=  vma->vm_start)
650                         break;
651                 if (vma->vm_flags & VM_LOCKED) {
652                         if (start > vma->vm_start)
653                                 count -= (start - vma->vm_start);
654                         if (start + len < vma->vm_end) {
655                                 count += start + len - vma->vm_start;
656                                 break;
657                         }
658                         count += vma->vm_end - vma->vm_start;
659                 }
660         }
661 
662         return count >> PAGE_SHIFT;
663 }
664 
665 static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
666 {
667         unsigned long locked;
668         unsigned long lock_limit;
669         int error = -ENOMEM;
670 
671         if (!can_do_mlock())
672                 return -EPERM;
673 
674         lru_add_drain_all();    /* flush pagevec */
675 
676         len = PAGE_ALIGN(len + (offset_in_page(start)));
677         start &= PAGE_MASK;
678 
679         lock_limit = rlimit(RLIMIT_MEMLOCK);
680         lock_limit >>= PAGE_SHIFT;
681         locked = len >> PAGE_SHIFT;
682 
683         if (down_write_killable(&current->mm->mmap_sem))
684                 return -EINTR;
685 
686         locked += current->mm->locked_vm;
687         if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
688                 /*
689                  * It is possible that the regions requested intersect with
690                  * previously mlocked areas, that part area in "mm->locked_vm"
691                  * should not be counted to new mlock increment count. So check
692                  * and adjust locked count if necessary.
693                  */
694                 locked -= count_mm_mlocked_page_nr(current->mm,
695                                 start, len);
696         }
697 
698         /* check against resource limits */
699         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
700                 error = apply_vma_lock_flags(start, len, flags);
701 
702         up_write(&current->mm->mmap_sem);
703         if (error)
704                 return error;
705 
706         error = __mm_populate(start, len, 0);
707         if (error)
708                 return __mlock_posix_error_return(error);
709         return 0;
710 }
711 
712 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
713 {
714         return do_mlock(start, len, VM_LOCKED);
715 }
716 
717 SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
718 {
719         vm_flags_t vm_flags = VM_LOCKED;
720 
721         if (flags & ~MLOCK_ONFAULT)
722                 return -EINVAL;
723 
724         if (flags & MLOCK_ONFAULT)
725                 vm_flags |= VM_LOCKONFAULT;
726 
727         return do_mlock(start, len, vm_flags);
728 }
729 
730 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
731 {
732         int ret;
733 
734         len = PAGE_ALIGN(len + (offset_in_page(start)));
735         start &= PAGE_MASK;
736 
737         if (down_write_killable(&current->mm->mmap_sem))
738                 return -EINTR;
739         ret = apply_vma_lock_flags(start, len, 0);
740         up_write(&current->mm->mmap_sem);
741 
742         return ret;
743 }
744 
745 /*
746  * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
747  * and translate into the appropriate modifications to mm->def_flags and/or the
748  * flags for all current VMAs.
749  *
750  * There are a couple of subtleties with this.  If mlockall() is called multiple
751  * times with different flags, the values do not necessarily stack.  If mlockall
752  * is called once including the MCL_FUTURE flag and then a second time without
753  * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
754  */
755 static int apply_mlockall_flags(int flags)
756 {
757         struct vm_area_struct * vma, * prev = NULL;
758         vm_flags_t to_add = 0;
759 
760         current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
761         if (flags & MCL_FUTURE) {
762                 current->mm->def_flags |= VM_LOCKED;
763 
764                 if (flags & MCL_ONFAULT)
765                         current->mm->def_flags |= VM_LOCKONFAULT;
766 
767                 if (!(flags & MCL_CURRENT))
768                         goto out;
769         }
770 
771         if (flags & MCL_CURRENT) {
772                 to_add |= VM_LOCKED;
773                 if (flags & MCL_ONFAULT)
774                         to_add |= VM_LOCKONFAULT;
775         }
776 
777         for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
778                 vm_flags_t newflags;
779 
780                 newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
781                 newflags |= to_add;
782 
783                 /* Ignore errors */
784                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
785                 cond_resched_rcu_qs();
786         }
787 out:
788         return 0;
789 }
790 
791 SYSCALL_DEFINE1(mlockall, int, flags)
792 {
793         unsigned long lock_limit;
794         int ret;
795 
796         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)))
797                 return -EINVAL;
798 
799         if (!can_do_mlock())
800                 return -EPERM;
801 
802         if (flags & MCL_CURRENT)
803                 lru_add_drain_all();    /* flush pagevec */
804 
805         lock_limit = rlimit(RLIMIT_MEMLOCK);
806         lock_limit >>= PAGE_SHIFT;
807 
808         if (down_write_killable(&current->mm->mmap_sem))
809                 return -EINTR;
810 
811         ret = -ENOMEM;
812         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
813             capable(CAP_IPC_LOCK))
814                 ret = apply_mlockall_flags(flags);
815         up_write(&current->mm->mmap_sem);
816         if (!ret && (flags & MCL_CURRENT))
817                 mm_populate(0, TASK_SIZE);
818 
819         return ret;
820 }
821 
822 SYSCALL_DEFINE0(munlockall)
823 {
824         int ret;
825 
826         if (down_write_killable(&current->mm->mmap_sem))
827                 return -EINTR;
828         ret = apply_mlockall_flags(0);
829         up_write(&current->mm->mmap_sem);
830         return ret;
831 }
832 
833 /*
834  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
835  * shm segments) get accounted against the user_struct instead.
836  */
837 static DEFINE_SPINLOCK(shmlock_user_lock);
838 
839 int user_shm_lock(size_t size, struct user_struct *user)
840 {
841         unsigned long lock_limit, locked;
842         int allowed = 0;
843 
844         locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
845         lock_limit = rlimit(RLIMIT_MEMLOCK);
846         if (lock_limit == RLIM_INFINITY)
847                 allowed = 1;
848         lock_limit >>= PAGE_SHIFT;
849         spin_lock(&shmlock_user_lock);
850         if (!allowed &&
851             locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
852                 goto out;
853         get_uid(user);
854         user->locked_shm += locked;
855         allowed = 1;
856 out:
857         spin_unlock(&shmlock_user_lock);
858         return allowed;
859 }
860 
861 void user_shm_unlock(size_t size, struct user_struct *user)
862 {
863         spin_lock(&shmlock_user_lock);
864         user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
865         spin_unlock(&shmlock_user_lock);
866         free_uid(user);
867 }
868 

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