source: src/linux/universal/linux-4.9/mm/mlock.c @ 31662

Last change on this file since 31662 was 31662, checked in by brainslayer, 6 weeks ago

use new squashfs in all kernels

File size: 22.5 KB
Line 
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(&current->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(&current->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(&current->mm->mmap_sem))
737                return -EINTR;
738        ret = apply_vma_lock_flags(start, len, 0);
739        up_write(&current->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(&current->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(&current->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(&current->mm->mmap_sem))
826                return -EINTR;
827        ret = apply_mlockall_flags(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 */
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}
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