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Linux/mm/mlock.c

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  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 int can_do_mlock(void)
 28 {
 29         if (capable(CAP_IPC_LOCK))
 30                 return 1;
 31         if (rlimit(RLIMIT_MEMLOCK) != 0)
 32                 return 1;
 33         return 0;
 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         if (!TestSetPageMlocked(page)) {
 86                 mod_zone_page_state(page_zone(page), NR_MLOCK,
 87                                     hpage_nr_pages(page));
 88                 count_vm_event(UNEVICTABLE_PGMLOCKED);
 89                 if (!isolate_lru_page(page))
 90                         putback_lru_page(page);
 91         }
 92 }
 93 
 94 /*
 95  * Isolate a page from LRU with optional get_page() pin.
 96  * Assumes lru_lock already held and page already pinned.
 97  */
 98 static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
 99 {
100         if (PageLRU(page)) {
101                 struct lruvec *lruvec;
102 
103                 lruvec = mem_cgroup_page_lruvec(page, page_zone(page));
104                 if (getpage)
105                         get_page(page);
106                 ClearPageLRU(page);
107                 del_page_from_lru_list(page, lruvec, page_lru(page));
108                 return true;
109         }
110 
111         return false;
112 }
113 
114 /*
115  * Finish munlock after successful page isolation
116  *
117  * Page must be locked. This is a wrapper for try_to_munlock()
118  * and putback_lru_page() with munlock accounting.
119  */
120 static void __munlock_isolated_page(struct page *page)
121 {
122         int ret = SWAP_AGAIN;
123 
124         /*
125          * Optimization: if the page was mapped just once, that's our mapping
126          * and we don't need to check all the other vmas.
127          */
128         if (page_mapcount(page) > 1)
129                 ret = try_to_munlock(page);
130 
131         /* Did try_to_unlock() succeed or punt? */
132         if (ret != SWAP_MLOCK)
133                 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
134 
135         putback_lru_page(page);
136 }
137 
138 /*
139  * Accounting for page isolation fail during munlock
140  *
141  * Performs accounting when page isolation fails in munlock. There is nothing
142  * else to do because it means some other task has already removed the page
143  * from the LRU. putback_lru_page() will take care of removing the page from
144  * the unevictable list, if necessary. vmscan [page_referenced()] will move
145  * the page back to the unevictable list if some other vma has it mlocked.
146  */
147 static void __munlock_isolation_failed(struct page *page)
148 {
149         if (PageUnevictable(page))
150                 __count_vm_event(UNEVICTABLE_PGSTRANDED);
151         else
152                 __count_vm_event(UNEVICTABLE_PGMUNLOCKED);
153 }
154 
155 /**
156  * munlock_vma_page - munlock a vma page
157  * @page - page to be unlocked, either a normal page or THP page head
158  *
159  * returns the size of the page as a page mask (0 for normal page,
160  *         HPAGE_PMD_NR - 1 for THP head page)
161  *
162  * called from munlock()/munmap() path with page supposedly on the LRU.
163  * When we munlock a page, because the vma where we found the page is being
164  * munlock()ed or munmap()ed, we want to check whether other vmas hold the
165  * page locked so that we can leave it on the unevictable lru list and not
166  * bother vmscan with it.  However, to walk the page's rmap list in
167  * try_to_munlock() we must isolate the page from the LRU.  If some other
168  * task has removed the page from the LRU, we won't be able to do that.
169  * So we clear the PageMlocked as we might not get another chance.  If we
170  * can't isolate the page, we leave it for putback_lru_page() and vmscan
171  * [page_referenced()/try_to_unmap()] to deal with.
172  */
173 unsigned int munlock_vma_page(struct page *page)
174 {
175         unsigned int nr_pages;
176         struct zone *zone = page_zone(page);
177 
178         /* For try_to_munlock() and to serialize with page migration */
179         BUG_ON(!PageLocked(page));
180 
181         /*
182          * Serialize with any parallel __split_huge_page_refcount() which
183          * might otherwise copy PageMlocked to part of the tail pages before
184          * we clear it in the head page. It also stabilizes hpage_nr_pages().
185          */
186         spin_lock_irq(&zone->lru_lock);
187 
188         nr_pages = hpage_nr_pages(page);
189         if (!TestClearPageMlocked(page))
190                 goto unlock_out;
191 
192         __mod_zone_page_state(zone, NR_MLOCK, -nr_pages);
193 
194         if (__munlock_isolate_lru_page(page, true)) {
195                 spin_unlock_irq(&zone->lru_lock);
196                 __munlock_isolated_page(page);
197                 goto out;
198         }
199         __munlock_isolation_failed(page);
200 
201 unlock_out:
202         spin_unlock_irq(&zone->lru_lock);
203 
204 out:
205         return nr_pages - 1;
206 }
207 
208 /**
209  * __mlock_vma_pages_range() -  mlock a range of pages in the vma.
210  * @vma:   target vma
211  * @start: start address
212  * @end:   end address
213  *
214  * This takes care of making the pages present too.
215  *
216  * return 0 on success, negative error code on error.
217  *
218  * vma->vm_mm->mmap_sem must be held for at least read.
219  */
220 long __mlock_vma_pages_range(struct vm_area_struct *vma,
221                 unsigned long start, unsigned long end, int *nonblocking)
222 {
223         struct mm_struct *mm = vma->vm_mm;
224         unsigned long nr_pages = (end - start) / PAGE_SIZE;
225         int gup_flags;
226 
227         VM_BUG_ON(start & ~PAGE_MASK);
228         VM_BUG_ON(end   & ~PAGE_MASK);
229         VM_BUG_ON(start < vma->vm_start);
230         VM_BUG_ON(end   > vma->vm_end);
231         VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
232 
233         gup_flags = FOLL_TOUCH | FOLL_MLOCK;
234         /*
235          * We want to touch writable mappings with a write fault in order
236          * to break COW, except for shared mappings because these don't COW
237          * and we would not want to dirty them for nothing.
238          */
239         if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
240                 gup_flags |= FOLL_WRITE;
241 
242         /*
243          * We want mlock to succeed for regions that have any permissions
244          * other than PROT_NONE.
245          */
246         if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
247                 gup_flags |= FOLL_FORCE;
248 
249         /*
250          * We made sure addr is within a VMA, so the following will
251          * not result in a stack expansion that recurses back here.
252          */
253         return __get_user_pages(current, mm, start, nr_pages, gup_flags,
254                                 NULL, NULL, nonblocking);
255 }
256 
257 /*
258  * convert get_user_pages() return value to posix mlock() error
259  */
260 static int __mlock_posix_error_return(long retval)
261 {
262         if (retval == -EFAULT)
263                 retval = -ENOMEM;
264         else if (retval == -ENOMEM)
265                 retval = -EAGAIN;
266         return retval;
267 }
268 
269 /*
270  * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
271  *
272  * The fast path is available only for evictable pages with single mapping.
273  * Then we can bypass the per-cpu pvec and get better performance.
274  * when mapcount > 1 we need try_to_munlock() which can fail.
275  * when !page_evictable(), we need the full redo logic of putback_lru_page to
276  * avoid leaving evictable page in unevictable list.
277  *
278  * In case of success, @page is added to @pvec and @pgrescued is incremented
279  * in case that the page was previously unevictable. @page is also unlocked.
280  */
281 static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
282                 int *pgrescued)
283 {
284         VM_BUG_ON_PAGE(PageLRU(page), page);
285         VM_BUG_ON_PAGE(!PageLocked(page), page);
286 
287         if (page_mapcount(page) <= 1 && page_evictable(page)) {
288                 pagevec_add(pvec, page);
289                 if (TestClearPageUnevictable(page))
290                         (*pgrescued)++;
291                 unlock_page(page);
292                 return true;
293         }
294 
295         return false;
296 }
297 
298 /*
299  * Putback multiple evictable pages to the LRU
300  *
301  * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
302  * the pages might have meanwhile become unevictable but that is OK.
303  */
304 static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
305 {
306         count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
307         /*
308          *__pagevec_lru_add() calls release_pages() so we don't call
309          * put_page() explicitly
310          */
311         __pagevec_lru_add(pvec);
312         count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
313 }
314 
315 /*
316  * Munlock a batch of pages from the same zone
317  *
318  * The work is split to two main phases. First phase clears the Mlocked flag
319  * and attempts to isolate the pages, all under a single zone lru lock.
320  * The second phase finishes the munlock only for pages where isolation
321  * succeeded.
322  *
323  * Note that the pagevec may be modified during the process.
324  */
325 static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
326 {
327         int i;
328         int nr = pagevec_count(pvec);
329         int delta_munlocked;
330         struct pagevec pvec_putback;
331         int pgrescued = 0;
332 
333         pagevec_init(&pvec_putback, 0);
334 
335         /* Phase 1: page isolation */
336         spin_lock_irq(&zone->lru_lock);
337         for (i = 0; i < nr; i++) {
338                 struct page *page = pvec->pages[i];
339 
340                 if (TestClearPageMlocked(page)) {
341                         /*
342                          * We already have pin from follow_page_mask()
343                          * so we can spare the get_page() here.
344                          */
345                         if (__munlock_isolate_lru_page(page, false))
346                                 continue;
347                         else
348                                 __munlock_isolation_failed(page);
349                 }
350 
351                 /*
352                  * We won't be munlocking this page in the next phase
353                  * but we still need to release the follow_page_mask()
354                  * pin. We cannot do it under lru_lock however. If it's
355                  * the last pin, __page_cache_release() would deadlock.
356                  */
357                 pagevec_add(&pvec_putback, pvec->pages[i]);
358                 pvec->pages[i] = NULL;
359         }
360         delta_munlocked = -nr + pagevec_count(&pvec_putback);
361         __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
362         spin_unlock_irq(&zone->lru_lock);
363 
364         /* Now we can release pins of pages that we are not munlocking */
365         pagevec_release(&pvec_putback);
366 
367         /* Phase 2: page munlock */
368         for (i = 0; i < nr; i++) {
369                 struct page *page = pvec->pages[i];
370 
371                 if (page) {
372                         lock_page(page);
373                         if (!__putback_lru_fast_prepare(page, &pvec_putback,
374                                         &pgrescued)) {
375                                 /*
376                                  * Slow path. We don't want to lose the last
377                                  * pin before unlock_page()
378                                  */
379                                 get_page(page); /* for putback_lru_page() */
380                                 __munlock_isolated_page(page);
381                                 unlock_page(page);
382                                 put_page(page); /* from follow_page_mask() */
383                         }
384                 }
385         }
386 
387         /*
388          * Phase 3: page putback for pages that qualified for the fast path
389          * This will also call put_page() to return pin from follow_page_mask()
390          */
391         if (pagevec_count(&pvec_putback))
392                 __putback_lru_fast(&pvec_putback, pgrescued);
393 }
394 
395 /*
396  * Fill up pagevec for __munlock_pagevec using pte walk
397  *
398  * The function expects that the struct page corresponding to @start address is
399  * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
400  *
401  * The rest of @pvec is filled by subsequent pages within the same pmd and same
402  * zone, as long as the pte's are present and vm_normal_page() succeeds. These
403  * pages also get pinned.
404  *
405  * Returns the address of the next page that should be scanned. This equals
406  * @start + PAGE_SIZE when no page could be added by the pte walk.
407  */
408 static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
409                 struct vm_area_struct *vma, int zoneid, unsigned long start,
410                 unsigned long end)
411 {
412         pte_t *pte;
413         spinlock_t *ptl;
414 
415         /*
416          * Initialize pte walk starting at the already pinned page where we
417          * are sure that there is a pte, as it was pinned under the same
418          * mmap_sem write op.
419          */
420         pte = get_locked_pte(vma->vm_mm, start, &ptl);
421         /* Make sure we do not cross the page table boundary */
422         end = pgd_addr_end(start, end);
423         end = pud_addr_end(start, end);
424         end = pmd_addr_end(start, end);
425 
426         /* The page next to the pinned page is the first we will try to get */
427         start += PAGE_SIZE;
428         while (start < end) {
429                 struct page *page = NULL;
430                 pte++;
431                 if (pte_present(*pte))
432                         page = vm_normal_page(vma, start, *pte);
433                 /*
434                  * Break if page could not be obtained or the page's node+zone does not
435                  * match
436                  */
437                 if (!page || page_zone_id(page) != zoneid)
438                         break;
439 
440                 get_page(page);
441                 /*
442                  * Increase the address that will be returned *before* the
443                  * eventual break due to pvec becoming full by adding the page
444                  */
445                 start += PAGE_SIZE;
446                 if (pagevec_add(pvec, page) == 0)
447                         break;
448         }
449         pte_unmap_unlock(pte, ptl);
450         return start;
451 }
452 
453 /*
454  * munlock_vma_pages_range() - munlock all pages in the vma range.'
455  * @vma - vma containing range to be munlock()ed.
456  * @start - start address in @vma of the range
457  * @end - end of range in @vma.
458  *
459  *  For mremap(), munmap() and exit().
460  *
461  * Called with @vma VM_LOCKED.
462  *
463  * Returns with VM_LOCKED cleared.  Callers must be prepared to
464  * deal with this.
465  *
466  * We don't save and restore VM_LOCKED here because pages are
467  * still on lru.  In unmap path, pages might be scanned by reclaim
468  * and re-mlocked by try_to_{munlock|unmap} before we unmap and
469  * free them.  This will result in freeing mlocked pages.
470  */
471 void munlock_vma_pages_range(struct vm_area_struct *vma,
472                              unsigned long start, unsigned long end)
473 {
474         vma->vm_flags &= ~VM_LOCKED;
475 
476         while (start < end) {
477                 struct page *page = NULL;
478                 unsigned int page_mask;
479                 unsigned long page_increm;
480                 struct pagevec pvec;
481                 struct zone *zone;
482                 int zoneid;
483 
484                 pagevec_init(&pvec, 0);
485                 /*
486                  * Although FOLL_DUMP is intended for get_dump_page(),
487                  * it just so happens that its special treatment of the
488                  * ZERO_PAGE (returning an error instead of doing get_page)
489                  * suits munlock very well (and if somehow an abnormal page
490                  * has sneaked into the range, we won't oops here: great).
491                  */
492                 page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
493                                 &page_mask);
494 
495                 if (page && !IS_ERR(page)) {
496                         if (PageTransHuge(page)) {
497                                 lock_page(page);
498                                 /*
499                                  * Any THP page found by follow_page_mask() may
500                                  * have gotten split before reaching
501                                  * munlock_vma_page(), so we need to recompute
502                                  * the page_mask here.
503                                  */
504                                 page_mask = munlock_vma_page(page);
505                                 unlock_page(page);
506                                 put_page(page); /* follow_page_mask() */
507                         } else {
508                                 /*
509                                  * Non-huge pages are handled in batches via
510                                  * pagevec. The pin from follow_page_mask()
511                                  * prevents them from collapsing by THP.
512                                  */
513                                 pagevec_add(&pvec, page);
514                                 zone = page_zone(page);
515                                 zoneid = page_zone_id(page);
516 
517                                 /*
518                                  * Try to fill the rest of pagevec using fast
519                                  * pte walk. This will also update start to
520                                  * the next page to process. Then munlock the
521                                  * pagevec.
522                                  */
523                                 start = __munlock_pagevec_fill(&pvec, vma,
524                                                 zoneid, start, end);
525                                 __munlock_pagevec(&pvec, zone);
526                                 goto next;
527                         }
528                 }
529                 /* It's a bug to munlock in the middle of a THP page */
530                 VM_BUG_ON((start >> PAGE_SHIFT) & page_mask);
531                 page_increm = 1 + page_mask;
532                 start += page_increm * PAGE_SIZE;
533 next:
534                 cond_resched();
535         }
536 }
537 
538 /*
539  * mlock_fixup  - handle mlock[all]/munlock[all] requests.
540  *
541  * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
542  * munlock is a no-op.  However, for some special vmas, we go ahead and
543  * populate the ptes.
544  *
545  * For vmas that pass the filters, merge/split as appropriate.
546  */
547 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
548         unsigned long start, unsigned long end, vm_flags_t newflags)
549 {
550         struct mm_struct *mm = vma->vm_mm;
551         pgoff_t pgoff;
552         int nr_pages;
553         int ret = 0;
554         int lock = !!(newflags & VM_LOCKED);
555 
556         if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
557             is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
558                 goto out;       /* don't set VM_LOCKED,  don't count */
559 
560         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
561         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
562                           vma->vm_file, pgoff, vma_policy(vma));
563         if (*prev) {
564                 vma = *prev;
565                 goto success;
566         }
567 
568         if (start != vma->vm_start) {
569                 ret = split_vma(mm, vma, start, 1);
570                 if (ret)
571                         goto out;
572         }
573 
574         if (end != vma->vm_end) {
575                 ret = split_vma(mm, vma, end, 0);
576                 if (ret)
577                         goto out;
578         }
579 
580 success:
581         /*
582          * Keep track of amount of locked VM.
583          */
584         nr_pages = (end - start) >> PAGE_SHIFT;
585         if (!lock)
586                 nr_pages = -nr_pages;
587         mm->locked_vm += nr_pages;
588 
589         /*
590          * vm_flags is protected by the mmap_sem held in write mode.
591          * It's okay if try_to_unmap_one unmaps a page just after we
592          * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
593          */
594 
595         if (lock)
596                 vma->vm_flags = newflags;
597         else
598                 munlock_vma_pages_range(vma, start, end);
599 
600 out:
601         *prev = vma;
602         return ret;
603 }
604 
605 static int do_mlock(unsigned long start, size_t len, int on)
606 {
607         unsigned long nstart, end, tmp;
608         struct vm_area_struct * vma, * prev;
609         int error;
610 
611         VM_BUG_ON(start & ~PAGE_MASK);
612         VM_BUG_ON(len != PAGE_ALIGN(len));
613         end = start + len;
614         if (end < start)
615                 return -EINVAL;
616         if (end == start)
617                 return 0;
618         vma = find_vma(current->mm, start);
619         if (!vma || vma->vm_start > start)
620                 return -ENOMEM;
621 
622         prev = vma->vm_prev;
623         if (start > vma->vm_start)
624                 prev = vma;
625 
626         for (nstart = start ; ; ) {
627                 vm_flags_t newflags;
628 
629                 /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
630 
631                 newflags = vma->vm_flags & ~VM_LOCKED;
632                 if (on)
633                         newflags |= VM_LOCKED;
634 
635                 tmp = vma->vm_end;
636                 if (tmp > end)
637                         tmp = end;
638                 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
639                 if (error)
640                         break;
641                 nstart = tmp;
642                 if (nstart < prev->vm_end)
643                         nstart = prev->vm_end;
644                 if (nstart >= end)
645                         break;
646 
647                 vma = prev->vm_next;
648                 if (!vma || vma->vm_start != nstart) {
649                         error = -ENOMEM;
650                         break;
651                 }
652         }
653         return error;
654 }
655 
656 /*
657  * __mm_populate - populate and/or mlock pages within a range of address space.
658  *
659  * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
660  * flags. VMAs must be already marked with the desired vm_flags, and
661  * mmap_sem must not be held.
662  */
663 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
664 {
665         struct mm_struct *mm = current->mm;
666         unsigned long end, nstart, nend;
667         struct vm_area_struct *vma = NULL;
668         int locked = 0;
669         long ret = 0;
670 
671         VM_BUG_ON(start & ~PAGE_MASK);
672         VM_BUG_ON(len != PAGE_ALIGN(len));
673         end = start + len;
674 
675         for (nstart = start; nstart < end; nstart = nend) {
676                 /*
677                  * We want to fault in pages for [nstart; end) address range.
678                  * Find first corresponding VMA.
679                  */
680                 if (!locked) {
681                         locked = 1;
682                         down_read(&mm->mmap_sem);
683                         vma = find_vma(mm, nstart);
684                 } else if (nstart >= vma->vm_end)
685                         vma = vma->vm_next;
686                 if (!vma || vma->vm_start >= end)
687                         break;
688                 /*
689                  * Set [nstart; nend) to intersection of desired address
690                  * range with the first VMA. Also, skip undesirable VMA types.
691                  */
692                 nend = min(end, vma->vm_end);
693                 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
694                         continue;
695                 if (nstart < vma->vm_start)
696                         nstart = vma->vm_start;
697                 /*
698                  * Now fault in a range of pages. __mlock_vma_pages_range()
699                  * double checks the vma flags, so that it won't mlock pages
700                  * if the vma was already munlocked.
701                  */
702                 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
703                 if (ret < 0) {
704                         if (ignore_errors) {
705                                 ret = 0;
706                                 continue;       /* continue at next VMA */
707                         }
708                         ret = __mlock_posix_error_return(ret);
709                         break;
710                 }
711                 nend = nstart + ret * PAGE_SIZE;
712                 ret = 0;
713         }
714         if (locked)
715                 up_read(&mm->mmap_sem);
716         return ret;     /* 0 or negative error code */
717 }
718 
719 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
720 {
721         unsigned long locked;
722         unsigned long lock_limit;
723         int error = -ENOMEM;
724 
725         if (!can_do_mlock())
726                 return -EPERM;
727 
728         lru_add_drain_all();    /* flush pagevec */
729 
730         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
731         start &= PAGE_MASK;
732 
733         lock_limit = rlimit(RLIMIT_MEMLOCK);
734         lock_limit >>= PAGE_SHIFT;
735         locked = len >> PAGE_SHIFT;
736 
737         down_write(&current->mm->mmap_sem);
738 
739         locked += current->mm->locked_vm;
740 
741         /* check against resource limits */
742         if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
743                 error = do_mlock(start, len, 1);
744 
745         up_write(&current->mm->mmap_sem);
746         if (!error)
747                 error = __mm_populate(start, len, 0);
748         return error;
749 }
750 
751 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
752 {
753         int ret;
754 
755         len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
756         start &= PAGE_MASK;
757 
758         down_write(&current->mm->mmap_sem);
759         ret = do_mlock(start, len, 0);
760         up_write(&current->mm->mmap_sem);
761 
762         return ret;
763 }
764 
765 static int do_mlockall(int flags)
766 {
767         struct vm_area_struct * vma, * prev = NULL;
768 
769         if (flags & MCL_FUTURE)
770                 current->mm->def_flags |= VM_LOCKED;
771         else
772                 current->mm->def_flags &= ~VM_LOCKED;
773         if (flags == MCL_FUTURE)
774                 goto out;
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;
780                 if (flags & MCL_CURRENT)
781                         newflags |= VM_LOCKED;
782 
783                 /* Ignore errors */
784                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
785                 cond_resched();
786         }
787 out:
788         return 0;
789 }
790 
791 SYSCALL_DEFINE1(mlockall, int, flags)
792 {
793         unsigned long lock_limit;
794         int ret = -EINVAL;
795 
796         if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
797                 goto out;
798 
799         ret = -EPERM;
800         if (!can_do_mlock())
801                 goto out;
802 
803         if (flags & MCL_CURRENT)
804                 lru_add_drain_all();    /* flush pagevec */
805 
806         lock_limit = rlimit(RLIMIT_MEMLOCK);
807         lock_limit >>= PAGE_SHIFT;
808 
809         ret = -ENOMEM;
810         down_write(&current->mm->mmap_sem);
811 
812         if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
813             capable(CAP_IPC_LOCK))
814                 ret = do_mlockall(flags);
815         up_write(&current->mm->mmap_sem);
816         if (!ret && (flags & MCL_CURRENT))
817                 mm_populate(0, TASK_SIZE);
818 out:
819         return ret;
820 }
821 
822 SYSCALL_DEFINE0(munlockall)
823 {
824         int ret;
825 
826         down_write(&current->mm->mmap_sem);
827         ret = do_mlockall(0);
828         up_write(&current->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  */
836 static DEFINE_SPINLOCK(shmlock_user_lock);
837 
838 int 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;
855 out:
856         spin_unlock(&shmlock_user_lock);
857         return allowed;
858 }
859 
860 void 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 }
867 

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