4 * (C) Copyright 1995 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
8 #include <linux/capability.h>
9 #include <linux/mman.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>
27 int can_do_mlock(void)
29 if (capable(CAP_IPC_LOCK))
31 if (rlimit(RLIMIT_MEMLOCK) != 0)
35 EXPORT_SYMBOL(can_do_mlock);
38 * Mlocked pages are marked with PageMlocked() flag for efficient testing
39 * in vmscan and, possibly, the fault path; and to support semi-accurate
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.
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
55 * LRU accounting for clear_page_mlock()
57 void clear_page_mlock(struct page *page)
59 if (!TestClearPageMlocked(page))
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);
69 * We lost the race. the page already moved to evictable list.
71 if (PageUnevictable(page))
72 count_vm_event(UNEVICTABLE_PGSTRANDED);
77 * Mark page as mlocked if not already.
78 * If page on LRU, isolate and putback to move to unevictable list.
80 void mlock_vma_page(struct page *page)
82 BUG_ON(!PageLocked(page));
84 if (!TestSetPageMlocked(page)) {
85 mod_zone_page_state(page_zone(page), NR_MLOCK,
86 hpage_nr_pages(page));
87 count_vm_event(UNEVICTABLE_PGMLOCKED);
88 if (!isolate_lru_page(page))
89 putback_lru_page(page);
94 * Finish munlock after successful page isolation
96 * Page must be locked. This is a wrapper for try_to_munlock()
97 * and putback_lru_page() with munlock accounting.
99 static void __munlock_isolated_page(struct page *page)
101 int ret = SWAP_AGAIN;
104 * Optimization: if the page was mapped just once, that's our mapping
105 * and we don't need to check all the other vmas.
107 if (page_mapcount(page) > 1)
108 ret = try_to_munlock(page);
110 /* Did try_to_unlock() succeed or punt? */
111 if (ret != SWAP_MLOCK)
112 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
114 putback_lru_page(page);
118 * Accounting for page isolation fail during munlock
120 * Performs accounting when page isolation fails in munlock. There is nothing
121 * else to do because it means some other task has already removed the page
122 * from the LRU. putback_lru_page() will take care of removing the page from
123 * the unevictable list, if necessary. vmscan [page_referenced()] will move
124 * the page back to the unevictable list if some other vma has it mlocked.
126 static void __munlock_isolation_failed(struct page *page)
128 if (PageUnevictable(page))
129 count_vm_event(UNEVICTABLE_PGSTRANDED);
131 count_vm_event(UNEVICTABLE_PGMUNLOCKED);
135 * munlock_vma_page - munlock a vma page
136 * @page - page to be unlocked, either a normal page or THP page head
138 * returns the size of the page as a page mask (0 for normal page,
139 * HPAGE_PMD_NR - 1 for THP head page)
141 * called from munlock()/munmap() path with page supposedly on the LRU.
142 * When we munlock a page, because the vma where we found the page is being
143 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
144 * page locked so that we can leave it on the unevictable lru list and not
145 * bother vmscan with it. However, to walk the page's rmap list in
146 * try_to_munlock() we must isolate the page from the LRU. If some other
147 * task has removed the page from the LRU, we won't be able to do that.
148 * So we clear the PageMlocked as we might not get another chance. If we
149 * can't isolate the page, we leave it for putback_lru_page() and vmscan
150 * [page_referenced()/try_to_unmap()] to deal with.
152 unsigned int munlock_vma_page(struct page *page)
154 unsigned int nr_pages;
156 BUG_ON(!PageLocked(page));
158 if (TestClearPageMlocked(page)) {
159 nr_pages = hpage_nr_pages(page);
160 mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
161 if (!isolate_lru_page(page))
162 __munlock_isolated_page(page);
164 __munlock_isolation_failed(page);
166 nr_pages = hpage_nr_pages(page);
170 * Regardless of the original PageMlocked flag, we determine nr_pages
171 * after touching the flag. This leaves a possible race with a THP page
172 * split, such that a whole THP page was munlocked, but nr_pages == 1.
173 * Returning a smaller mask due to that is OK, the worst that can
174 * happen is subsequent useless scanning of the former tail pages.
175 * The NR_MLOCK accounting can however become broken.
181 * __mlock_vma_pages_range() - mlock a range of pages in the vma.
183 * @start: start address
186 * This takes care of making the pages present too.
188 * return 0 on success, negative error code on error.
190 * vma->vm_mm->mmap_sem must be held for at least read.
192 long __mlock_vma_pages_range(struct vm_area_struct *vma,
193 unsigned long start, unsigned long end, int *nonblocking)
195 struct mm_struct *mm = vma->vm_mm;
196 unsigned long nr_pages = (end - start) / PAGE_SIZE;
199 VM_BUG_ON(start & ~PAGE_MASK);
200 VM_BUG_ON(end & ~PAGE_MASK);
201 VM_BUG_ON(start < vma->vm_start);
202 VM_BUG_ON(end > vma->vm_end);
203 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
205 gup_flags = FOLL_TOUCH | FOLL_MLOCK;
207 * We want to touch writable mappings with a write fault in order
208 * to break COW, except for shared mappings because these don't COW
209 * and we would not want to dirty them for nothing.
211 if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
212 gup_flags |= FOLL_WRITE;
215 * We want mlock to succeed for regions that have any permissions
216 * other than PROT_NONE.
218 if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
219 gup_flags |= FOLL_FORCE;
222 * We made sure addr is within a VMA, so the following will
223 * not result in a stack expansion that recurses back here.
225 return __get_user_pages(current, mm, start, nr_pages, gup_flags,
226 NULL, NULL, nonblocking);
230 * convert get_user_pages() return value to posix mlock() error
232 static int __mlock_posix_error_return(long retval)
234 if (retval == -EFAULT)
236 else if (retval == -ENOMEM)
242 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
244 * The fast path is available only for evictable pages with single mapping.
245 * Then we can bypass the per-cpu pvec and get better performance.
246 * when mapcount > 1 we need try_to_munlock() which can fail.
247 * when !page_evictable(), we need the full redo logic of putback_lru_page to
248 * avoid leaving evictable page in unevictable list.
250 * In case of success, @page is added to @pvec and @pgrescued is incremented
251 * in case that the page was previously unevictable. @page is also unlocked.
253 static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
256 VM_BUG_ON(PageLRU(page));
257 VM_BUG_ON(!PageLocked(page));
259 if (page_mapcount(page) <= 1 && page_evictable(page)) {
260 pagevec_add(pvec, page);
261 if (TestClearPageUnevictable(page))
271 * Putback multiple evictable pages to the LRU
273 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
274 * the pages might have meanwhile become unevictable but that is OK.
276 static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
278 count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
280 *__pagevec_lru_add() calls release_pages() so we don't call
281 * put_page() explicitly
283 __pagevec_lru_add(pvec);
284 count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
288 * Munlock a batch of pages from the same zone
290 * The work is split to two main phases. First phase clears the Mlocked flag
291 * and attempts to isolate the pages, all under a single zone lru lock.
292 * The second phase finishes the munlock only for pages where isolation
295 * Note that the pagevec may be modified during the process.
297 static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
300 int nr = pagevec_count(pvec);
301 int delta_munlocked = -nr;
302 struct pagevec pvec_putback;
305 /* Phase 1: page isolation */
306 spin_lock_irq(&zone->lru_lock);
307 for (i = 0; i < nr; i++) {
308 struct page *page = pvec->pages[i];
310 if (TestClearPageMlocked(page)) {
311 struct lruvec *lruvec;
315 lruvec = mem_cgroup_page_lruvec(page, zone);
316 lru = page_lru(page);
318 * We already have pin from follow_page_mask()
319 * so we can spare the get_page() here.
322 del_page_from_lru_list(page, lruvec, lru);
324 __munlock_isolation_failed(page);
331 * We won't be munlocking this page in the next phase
332 * but we still need to release the follow_page_mask()
335 pvec->pages[i] = NULL;
340 __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
341 spin_unlock_irq(&zone->lru_lock);
343 /* Phase 2: page munlock */
344 pagevec_init(&pvec_putback, 0);
345 for (i = 0; i < nr; i++) {
346 struct page *page = pvec->pages[i];
350 if (!__putback_lru_fast_prepare(page, &pvec_putback,
353 * Slow path. We don't want to lose the last
354 * pin before unlock_page()
356 get_page(page); /* for putback_lru_page() */
357 __munlock_isolated_page(page);
359 put_page(page); /* from follow_page_mask() */
365 * Phase 3: page putback for pages that qualified for the fast path
366 * This will also call put_page() to return pin from follow_page_mask()
368 if (pagevec_count(&pvec_putback))
369 __putback_lru_fast(&pvec_putback, pgrescued);
373 * Fill up pagevec for __munlock_pagevec using pte walk
375 * The function expects that the struct page corresponding to @start address is
376 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
378 * The rest of @pvec is filled by subsequent pages within the same pmd and same
379 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
380 * pages also get pinned.
382 * Returns the address of the next page that should be scanned. This equals
383 * @start + PAGE_SIZE when no page could be added by the pte walk.
385 static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
386 struct vm_area_struct *vma, int zoneid, unsigned long start,
393 * Initialize pte walk starting at the already pinned page where we
394 * are sure that there is a pte, as it was pinned under the same
397 pte = get_locked_pte(vma->vm_mm, start, &ptl);
398 /* Make sure we do not cross the page table boundary */
399 end = pgd_addr_end(start, end);
400 end = pud_addr_end(start, end);
401 end = pmd_addr_end(start, end);
403 /* The page next to the pinned page is the first we will try to get */
405 while (start < end) {
406 struct page *page = NULL;
408 if (pte_present(*pte))
409 page = vm_normal_page(vma, start, *pte);
411 * Break if page could not be obtained or the page's node+zone does not
414 if (!page || page_zone_id(page) != zoneid)
419 * Increase the address that will be returned *before* the
420 * eventual break due to pvec becoming full by adding the page
423 if (pagevec_add(pvec, page) == 0)
426 pte_unmap_unlock(pte, ptl);
431 * munlock_vma_pages_range() - munlock all pages in the vma range.'
432 * @vma - vma containing range to be munlock()ed.
433 * @start - start address in @vma of the range
434 * @end - end of range in @vma.
436 * For mremap(), munmap() and exit().
438 * Called with @vma VM_LOCKED.
440 * Returns with VM_LOCKED cleared. Callers must be prepared to
443 * We don't save and restore VM_LOCKED here because pages are
444 * still on lru. In unmap path, pages might be scanned by reclaim
445 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
446 * free them. This will result in freeing mlocked pages.
448 void munlock_vma_pages_range(struct vm_area_struct *vma,
449 unsigned long start, unsigned long end)
451 vma->vm_flags &= ~VM_LOCKED;
453 while (start < end) {
454 struct page *page = NULL;
455 unsigned int page_mask;
456 unsigned long page_increm;
461 pagevec_init(&pvec, 0);
463 * Although FOLL_DUMP is intended for get_dump_page(),
464 * it just so happens that its special treatment of the
465 * ZERO_PAGE (returning an error instead of doing get_page)
466 * suits munlock very well (and if somehow an abnormal page
467 * has sneaked into the range, we won't oops here: great).
469 page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
472 if (page && !IS_ERR(page)) {
473 if (PageTransHuge(page)) {
476 * Any THP page found by follow_page_mask() may
477 * have gotten split before reaching
478 * munlock_vma_page(), so we need to recompute
479 * the page_mask here.
481 page_mask = munlock_vma_page(page);
483 put_page(page); /* follow_page_mask() */
486 * Non-huge pages are handled in batches via
487 * pagevec. The pin from follow_page_mask()
488 * prevents them from collapsing by THP.
490 pagevec_add(&pvec, page);
491 zone = page_zone(page);
492 zoneid = page_zone_id(page);
495 * Try to fill the rest of pagevec using fast
496 * pte walk. This will also update start to
497 * the next page to process. Then munlock the
500 start = __munlock_pagevec_fill(&pvec, vma,
502 __munlock_pagevec(&pvec, zone);
506 /* It's a bug to munlock in the middle of a THP page */
507 VM_BUG_ON((start >> PAGE_SHIFT) & page_mask);
508 page_increm = 1 + page_mask;
509 start += page_increm * PAGE_SIZE;
516 * mlock_fixup - handle mlock[all]/munlock[all] requests.
518 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
519 * munlock is a no-op. However, for some special vmas, we go ahead and
522 * For vmas that pass the filters, merge/split as appropriate.
524 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
525 unsigned long start, unsigned long end, vm_flags_t newflags)
527 struct mm_struct *mm = vma->vm_mm;
531 int lock = !!(newflags & VM_LOCKED);
533 if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
534 is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
535 goto out; /* don't set VM_LOCKED, don't count */
537 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
538 *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
539 vma->vm_file, pgoff, vma_policy(vma));
545 if (start != vma->vm_start) {
546 ret = split_vma(mm, vma, start, 1);
551 if (end != vma->vm_end) {
552 ret = split_vma(mm, vma, end, 0);
559 * Keep track of amount of locked VM.
561 nr_pages = (end - start) >> PAGE_SHIFT;
563 nr_pages = -nr_pages;
564 mm->locked_vm += nr_pages;
567 * vm_flags is protected by the mmap_sem held in write mode.
568 * It's okay if try_to_unmap_one unmaps a page just after we
569 * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
573 vma->vm_flags = newflags;
575 munlock_vma_pages_range(vma, start, end);
582 static int do_mlock(unsigned long start, size_t len, int on)
584 unsigned long nstart, end, tmp;
585 struct vm_area_struct * vma, * prev;
588 VM_BUG_ON(start & ~PAGE_MASK);
589 VM_BUG_ON(len != PAGE_ALIGN(len));
595 vma = find_vma(current->mm, start);
596 if (!vma || vma->vm_start > start)
600 if (start > vma->vm_start)
603 for (nstart = start ; ; ) {
606 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
608 newflags = vma->vm_flags & ~VM_LOCKED;
610 newflags |= VM_LOCKED;
615 error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
619 if (nstart < prev->vm_end)
620 nstart = prev->vm_end;
625 if (!vma || vma->vm_start != nstart) {
634 * __mm_populate - populate and/or mlock pages within a range of address space.
636 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
637 * flags. VMAs must be already marked with the desired vm_flags, and
638 * mmap_sem must not be held.
640 int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
642 struct mm_struct *mm = current->mm;
643 unsigned long end, nstart, nend;
644 struct vm_area_struct *vma = NULL;
648 VM_BUG_ON(start & ~PAGE_MASK);
649 VM_BUG_ON(len != PAGE_ALIGN(len));
652 for (nstart = start; nstart < end; nstart = nend) {
654 * We want to fault in pages for [nstart; end) address range.
655 * Find first corresponding VMA.
659 down_read(&mm->mmap_sem);
660 vma = find_vma(mm, nstart);
661 } else if (nstart >= vma->vm_end)
663 if (!vma || vma->vm_start >= end)
666 * Set [nstart; nend) to intersection of desired address
667 * range with the first VMA. Also, skip undesirable VMA types.
669 nend = min(end, vma->vm_end);
670 if (vma->vm_flags & (VM_IO | VM_PFNMAP))
672 if (nstart < vma->vm_start)
673 nstart = vma->vm_start;
675 * Now fault in a range of pages. __mlock_vma_pages_range()
676 * double checks the vma flags, so that it won't mlock pages
677 * if the vma was already munlocked.
679 ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
683 continue; /* continue at next VMA */
685 ret = __mlock_posix_error_return(ret);
688 nend = nstart + ret * PAGE_SIZE;
692 up_read(&mm->mmap_sem);
693 return ret; /* 0 or negative error code */
696 SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
698 unsigned long locked;
699 unsigned long lock_limit;
705 lru_add_drain_all(); /* flush pagevec */
707 down_write(¤t->mm->mmap_sem);
708 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
711 locked = len >> PAGE_SHIFT;
712 locked += current->mm->locked_vm;
714 lock_limit = rlimit(RLIMIT_MEMLOCK);
715 lock_limit >>= PAGE_SHIFT;
717 /* check against resource limits */
718 if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
719 error = do_mlock(start, len, 1);
720 up_write(¤t->mm->mmap_sem);
722 error = __mm_populate(start, len, 0);
726 SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
730 down_write(¤t->mm->mmap_sem);
731 len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
733 ret = do_mlock(start, len, 0);
734 up_write(¤t->mm->mmap_sem);
738 static int do_mlockall(int flags)
740 struct vm_area_struct * vma, * prev = NULL;
742 if (flags & MCL_FUTURE)
743 current->mm->def_flags |= VM_LOCKED;
745 current->mm->def_flags &= ~VM_LOCKED;
746 if (flags == MCL_FUTURE)
749 for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
752 newflags = vma->vm_flags & ~VM_LOCKED;
753 if (flags & MCL_CURRENT)
754 newflags |= VM_LOCKED;
757 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
764 SYSCALL_DEFINE1(mlockall, int, flags)
766 unsigned long lock_limit;
769 if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
776 if (flags & MCL_CURRENT)
777 lru_add_drain_all(); /* flush pagevec */
779 down_write(¤t->mm->mmap_sem);
781 lock_limit = rlimit(RLIMIT_MEMLOCK);
782 lock_limit >>= PAGE_SHIFT;
785 if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
786 capable(CAP_IPC_LOCK))
787 ret = do_mlockall(flags);
788 up_write(¤t->mm->mmap_sem);
789 if (!ret && (flags & MCL_CURRENT))
790 mm_populate(0, TASK_SIZE);
795 SYSCALL_DEFINE0(munlockall)
799 down_write(¤t->mm->mmap_sem);
800 ret = do_mlockall(0);
801 up_write(¤t->mm->mmap_sem);
806 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
807 * shm segments) get accounted against the user_struct instead.
809 static DEFINE_SPINLOCK(shmlock_user_lock);
811 int user_shm_lock(size_t size, struct user_struct *user)
813 unsigned long lock_limit, locked;
816 locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
817 lock_limit = rlimit(RLIMIT_MEMLOCK);
818 if (lock_limit == RLIM_INFINITY)
820 lock_limit >>= PAGE_SHIFT;
821 spin_lock(&shmlock_user_lock);
823 locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
826 user->locked_shm += locked;
829 spin_unlock(&shmlock_user_lock);
833 void user_shm_unlock(size_t size, struct user_struct *user)
835 spin_lock(&shmlock_user_lock);
836 user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
837 spin_unlock(&shmlock_user_lock);