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
  27int 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}
  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        BUG_ON(!PageLocked(page));
  83
  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);
  90        }
  91}
  92
  93/*
  94 * Finish munlock after successful page isolation
  95 *
  96 * Page must be locked. This is a wrapper for try_to_munlock()
  97 * and putback_lru_page() with munlock accounting.
  98 */
  99static void __munlock_isolated_page(struct page *page)
 100{
 101        int ret = SWAP_AGAIN;
 102
 103        /*
 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.
 106         */
 107        if (page_mapcount(page) > 1)
 108                ret = try_to_munlock(page);
 109
 110        /* Did try_to_unlock() succeed or punt? */
 111        if (ret != SWAP_MLOCK)
 112                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
 113
 114        putback_lru_page(page);
 115}
 116
 117/*
 118 * Accounting for page isolation fail during munlock
 119 *
 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.
 125 */
 126static void __munlock_isolation_failed(struct page *page)
 127{
 128        if (PageUnevictable(page))
 129                count_vm_event(UNEVICTABLE_PGSTRANDED);
 130        else
 131                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
 132}
 133
 134/**
 135 * munlock_vma_page - munlock a vma page
 136 * @page - page to be unlocked
 137 *
 138 * called from munlock()/munmap() path with page supposedly on the LRU.
 139 * When we munlock a page, because the vma where we found the page is being
 140 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
 141 * page locked so that we can leave it on the unevictable lru list and not
 142 * bother vmscan with it.  However, to walk the page's rmap list in
 143 * try_to_munlock() we must isolate the page from the LRU.  If some other
 144 * task has removed the page from the LRU, we won't be able to do that.
 145 * So we clear the PageMlocked as we might not get another chance.  If we
 146 * can't isolate the page, we leave it for putback_lru_page() and vmscan
 147 * [page_referenced()/try_to_unmap()] to deal with.
 148 */
 149unsigned int munlock_vma_page(struct page *page)
 150{
 151        unsigned int page_mask = 0;
 152
 153        BUG_ON(!PageLocked(page));
 154
 155        if (TestClearPageMlocked(page)) {
 156                unsigned int nr_pages = hpage_nr_pages(page);
 157                mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
 158                page_mask = nr_pages - 1;
 159                if (!isolate_lru_page(page))
 160                        __munlock_isolated_page(page);
 161                else
 162                        __munlock_isolation_failed(page);
 163        }
 164
 165        return page_mask;
 166}
 167
 168/**
 169 * __mlock_vma_pages_range() -  mlock a range of pages in the vma.
 170 * @vma:   target vma
 171 * @start: start address
 172 * @end:   end address
 173 *
 174 * This takes care of making the pages present too.
 175 *
 176 * return 0 on success, negative error code on error.
 177 *
 178 * vma->vm_mm->mmap_sem must be held for at least read.
 179 */
 180long __mlock_vma_pages_range(struct vm_area_struct *vma,
 181                unsigned long start, unsigned long end, int *nonblocking)
 182{
 183        struct mm_struct *mm = vma->vm_mm;
 184        unsigned long nr_pages = (end - start) / PAGE_SIZE;
 185        int gup_flags;
 186
 187        VM_BUG_ON(start & ~PAGE_MASK);
 188        VM_BUG_ON(end   & ~PAGE_MASK);
 189        VM_BUG_ON(start < vma->vm_start);
 190        VM_BUG_ON(end   > vma->vm_end);
 191        VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
 192
 193        gup_flags = FOLL_TOUCH | FOLL_MLOCK;
 194        /*
 195         * We want to touch writable mappings with a write fault in order
 196         * to break COW, except for shared mappings because these don't COW
 197         * and we would not want to dirty them for nothing.
 198         */
 199        if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
 200                gup_flags |= FOLL_WRITE;
 201
 202        /*
 203         * We want mlock to succeed for regions that have any permissions
 204         * other than PROT_NONE.
 205         */
 206        if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
 207                gup_flags |= FOLL_FORCE;
 208
 209        /*
 210         * We made sure addr is within a VMA, so the following will
 211         * not result in a stack expansion that recurses back here.
 212         */
 213        return __get_user_pages(current, mm, start, nr_pages, gup_flags,
 214                                NULL, NULL, nonblocking);
 215}
 216
 217/*
 218 * convert get_user_pages() return value to posix mlock() error
 219 */
 220static int __mlock_posix_error_return(long retval)
 221{
 222        if (retval == -EFAULT)
 223                retval = -ENOMEM;
 224        else if (retval == -ENOMEM)
 225                retval = -EAGAIN;
 226        return retval;
 227}
 228
 229/*
 230 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
 231 *
 232 * The fast path is available only for evictable pages with single mapping.
 233 * Then we can bypass the per-cpu pvec and get better performance.
 234 * when mapcount > 1 we need try_to_munlock() which can fail.
 235 * when !page_evictable(), we need the full redo logic of putback_lru_page to
 236 * avoid leaving evictable page in unevictable list.
 237 *
 238 * In case of success, @page is added to @pvec and @pgrescued is incremented
 239 * in case that the page was previously unevictable. @page is also unlocked.
 240 */
 241static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
 242                int *pgrescued)
 243{
 244        VM_BUG_ON(PageLRU(page));
 245        VM_BUG_ON(!PageLocked(page));
 246
 247        if (page_mapcount(page) <= 1 && page_evictable(page)) {
 248                pagevec_add(pvec, page);
 249                if (TestClearPageUnevictable(page))
 250                        (*pgrescued)++;
 251                unlock_page(page);
 252                return true;
 253        }
 254
 255        return false;
 256}
 257
 258/*
 259 * Putback multiple evictable pages to the LRU
 260 *
 261 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
 262 * the pages might have meanwhile become unevictable but that is OK.
 263 */
 264static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
 265{
 266        count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
 267        /*
 268         *__pagevec_lru_add() calls release_pages() so we don't call
 269         * put_page() explicitly
 270         */
 271        __pagevec_lru_add(pvec);
 272        count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
 273}
 274
 275/*
 276 * Munlock a batch of pages from the same zone
 277 *
 278 * The work is split to two main phases. First phase clears the Mlocked flag
 279 * and attempts to isolate the pages, all under a single zone lru lock.
 280 * The second phase finishes the munlock only for pages where isolation
 281 * succeeded.
 282 *
 283 * Note that the pagevec may be modified during the process.
 284 */
 285static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 286{
 287        int i;
 288        int nr = pagevec_count(pvec);
 289        int delta_munlocked = -nr;
 290        struct pagevec pvec_putback;
 291        int pgrescued = 0;
 292
 293        /* Phase 1: page isolation */
 294        spin_lock_irq(&zone->lru_lock);
 295        for (i = 0; i < nr; i++) {
 296                struct page *page = pvec->pages[i];
 297
 298                if (TestClearPageMlocked(page)) {
 299                        struct lruvec *lruvec;
 300                        int lru;
 301
 302                        if (PageLRU(page)) {
 303                                lruvec = mem_cgroup_page_lruvec(page, zone);
 304                                lru = page_lru(page);
 305                                /*
 306                                 * We already have pin from follow_page_mask()
 307                                 * so we can spare the get_page() here.
 308                                 */
 309                                ClearPageLRU(page);
 310                                del_page_from_lru_list(page, lruvec, lru);
 311                        } else {
 312                                __munlock_isolation_failed(page);
 313                                goto skip_munlock;
 314                        }
 315
 316                } else {
 317skip_munlock:
 318                        /*
 319                         * We won't be munlocking this page in the next phase
 320                         * but we still need to release the follow_page_mask()
 321                         * pin.
 322                         */
 323                        pvec->pages[i] = NULL;
 324                        put_page(page);
 325                        delta_munlocked++;
 326                }
 327        }
 328        __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
 329        spin_unlock_irq(&zone->lru_lock);
 330
 331        /* Phase 2: page munlock */
 332        pagevec_init(&pvec_putback, 0);
 333        for (i = 0; i < nr; i++) {
 334                struct page *page = pvec->pages[i];
 335
 336                if (page) {
 337                        lock_page(page);
 338                        if (!__putback_lru_fast_prepare(page, &pvec_putback,
 339                                        &pgrescued)) {
 340                                /*
 341                                 * Slow path. We don't want to lose the last
 342                                 * pin before unlock_page()
 343                                 */
 344                                get_page(page); /* for putback_lru_page() */
 345                                __munlock_isolated_page(page);
 346                                unlock_page(page);
 347                                put_page(page); /* from follow_page_mask() */
 348                        }
 349                }
 350        }
 351
 352        /*
 353         * Phase 3: page putback for pages that qualified for the fast path
 354         * This will also call put_page() to return pin from follow_page_mask()
 355         */
 356        if (pagevec_count(&pvec_putback))
 357                __putback_lru_fast(&pvec_putback, pgrescued);
 358}
 359
 360/*
 361 * Fill up pagevec for __munlock_pagevec using pte walk
 362 *
 363 * The function expects that the struct page corresponding to @start address is
 364 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
 365 *
 366 * The rest of @pvec is filled by subsequent pages within the same pmd and same
 367 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
 368 * pages also get pinned.
 369 *
 370 * Returns the address of the next page that should be scanned. This equals
 371 * @start + PAGE_SIZE when no page could be added by the pte walk.
 372 */
 373static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
 374                struct vm_area_struct *vma, int zoneid, unsigned long start,
 375                unsigned long end)
 376{
 377        pte_t *pte;
 378        spinlock_t *ptl;
 379
 380        /*
 381         * Initialize pte walk starting at the already pinned page where we
 382         * are sure that there is a pte, as it was pinned under the same
 383         * mmap_sem write op.
 384         */
 385        pte = get_locked_pte(vma->vm_mm, start, &ptl);
 386        /* Make sure we do not cross the page table boundary */
 387        end = pgd_addr_end(start, end);
 388        end = pud_addr_end(start, end);
 389        end = pmd_addr_end(start, end);
 390
 391        /* The page next to the pinned page is the first we will try to get */
 392        start += PAGE_SIZE;
 393        while (start < end) {
 394                struct page *page = NULL;
 395                pte++;
 396                if (pte_present(*pte))
 397                        page = vm_normal_page(vma, start, *pte);
 398                /*
 399                 * Break if page could not be obtained or the page's node+zone does not
 400                 * match
 401                 */
 402                if (!page || page_zone_id(page) != zoneid)
 403                        break;
 404
 405                get_page(page);
 406                /*
 407                 * Increase the address that will be returned *before* the
 408                 * eventual break due to pvec becoming full by adding the page
 409                 */
 410                start += PAGE_SIZE;
 411                if (pagevec_add(pvec, page) == 0)
 412                        break;
 413        }
 414        pte_unmap_unlock(pte, ptl);
 415        return start;
 416}
 417
 418/*
 419 * munlock_vma_pages_range() - munlock all pages in the vma range.'
 420 * @vma - vma containing range to be munlock()ed.
 421 * @start - start address in @vma of the range
 422 * @end - end of range in @vma.
 423 *
 424 *  For mremap(), munmap() and exit().
 425 *
 426 * Called with @vma VM_LOCKED.
 427 *
 428 * Returns with VM_LOCKED cleared.  Callers must be prepared to
 429 * deal with this.
 430 *
 431 * We don't save and restore VM_LOCKED here because pages are
 432 * still on lru.  In unmap path, pages might be scanned by reclaim
 433 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
 434 * free them.  This will result in freeing mlocked pages.
 435 */
 436void munlock_vma_pages_range(struct vm_area_struct *vma,
 437                             unsigned long start, unsigned long end)
 438{
 439        vma->vm_flags &= ~VM_LOCKED;
 440
 441        while (start < end) {
 442                struct page *page = NULL;
 443                unsigned int page_mask, page_increm;
 444                struct pagevec pvec;
 445                struct zone *zone;
 446                int zoneid;
 447
 448                pagevec_init(&pvec, 0);
 449                /*
 450                 * Although FOLL_DUMP is intended for get_dump_page(),
 451                 * it just so happens that its special treatment of the
 452                 * ZERO_PAGE (returning an error instead of doing get_page)
 453                 * suits munlock very well (and if somehow an abnormal page
 454                 * has sneaked into the range, we won't oops here: great).
 455                 */
 456                page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
 457                                &page_mask);
 458
 459                if (page && !IS_ERR(page)) {
 460                        if (PageTransHuge(page)) {
 461                                lock_page(page);
 462                                /*
 463                                 * Any THP page found by follow_page_mask() may
 464                                 * have gotten split before reaching
 465                                 * munlock_vma_page(), so we need to recompute
 466                                 * the page_mask here.
 467                                 */
 468                                page_mask = munlock_vma_page(page);
 469                                unlock_page(page);
 470                                put_page(page); /* follow_page_mask() */
 471                        } else {
 472                                /*
 473                                 * Non-huge pages are handled in batches via
 474                                 * pagevec. The pin from follow_page_mask()
 475                                 * prevents them from collapsing by THP.
 476                                 */
 477                                pagevec_add(&pvec, page);
 478                                zone = page_zone(page);
 479                                zoneid = page_zone_id(page);
 480
 481                                /*
 482                                 * Try to fill the rest of pagevec using fast
 483                                 * pte walk. This will also update start to
 484                                 * the next page to process. Then munlock the
 485                                 * pagevec.
 486                                 */
 487                                start = __munlock_pagevec_fill(&pvec, vma,
 488                                                zoneid, start, end);
 489                                __munlock_pagevec(&pvec, zone);
 490                                goto next;
 491                        }
 492                }
 493                page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
 494                start += page_increm * PAGE_SIZE;
 495next:
 496                cond_resched();
 497        }
 498}
 499
 500/*
 501 * mlock_fixup  - handle mlock[all]/munlock[all] requests.
 502 *
 503 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
 504 * munlock is a no-op.  However, for some special vmas, we go ahead and
 505 * populate the ptes.
 506 *
 507 * For vmas that pass the filters, merge/split as appropriate.
 508 */
 509static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 510        unsigned long start, unsigned long end, vm_flags_t newflags)
 511{
 512        struct mm_struct *mm = vma->vm_mm;
 513        pgoff_t pgoff;
 514        int nr_pages;
 515        int ret = 0;
 516        int lock = !!(newflags & VM_LOCKED);
 517
 518        if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
 519            is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
 520                goto out;       /* don't set VM_LOCKED,  don't count */
 521
 522        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 523        *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
 524                          vma->vm_file, pgoff, vma_policy(vma));
 525        if (*prev) {
 526                vma = *prev;
 527                goto success;
 528        }
 529
 530        if (start != vma->vm_start) {
 531                ret = split_vma(mm, vma, start, 1);
 532                if (ret)
 533                        goto out;
 534        }
 535
 536        if (end != vma->vm_end) {
 537                ret = split_vma(mm, vma, end, 0);
 538                if (ret)
 539                        goto out;
 540        }
 541
 542success:
 543        /*
 544         * Keep track of amount of locked VM.
 545         */
 546        nr_pages = (end - start) >> PAGE_SHIFT;
 547        if (!lock)
 548                nr_pages = -nr_pages;
 549        mm->locked_vm += nr_pages;
 550
 551        /*
 552         * vm_flags is protected by the mmap_sem held in write mode.
 553         * It's okay if try_to_unmap_one unmaps a page just after we
 554         * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
 555         */
 556
 557        if (lock)
 558                vma->vm_flags = newflags;
 559        else
 560                munlock_vma_pages_range(vma, start, end);
 561
 562out:
 563        *prev = vma;
 564        return ret;
 565}
 566
 567static int do_mlock(unsigned long start, size_t len, int on)
 568{
 569        unsigned long nstart, end, tmp;
 570        struct vm_area_struct * vma, * prev;
 571        int error;
 572
 573        VM_BUG_ON(start & ~PAGE_MASK);
 574        VM_BUG_ON(len != PAGE_ALIGN(len));
 575        end = start + len;
 576        if (end < start)
 577                return -EINVAL;
 578        if (end == start)
 579                return 0;
 580        vma = find_vma(current->mm, start);
 581        if (!vma || vma->vm_start > start)
 582                return -ENOMEM;
 583
 584        prev = vma->vm_prev;
 585        if (start > vma->vm_start)
 586                prev = vma;
 587
 588        for (nstart = start ; ; ) {
 589                vm_flags_t newflags;
 590
 591                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 592
 593                newflags = vma->vm_flags & ~VM_LOCKED;
 594                if (on)
 595                        newflags |= VM_LOCKED;
 596
 597                tmp = vma->vm_end;
 598                if (tmp > end)
 599                        tmp = end;
 600                error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 601                if (error)
 602                        break;
 603                nstart = tmp;
 604                if (nstart < prev->vm_end)
 605                        nstart = prev->vm_end;
 606                if (nstart >= end)
 607                        break;
 608
 609                vma = prev->vm_next;
 610                if (!vma || vma->vm_start != nstart) {
 611                        error = -ENOMEM;
 612                        break;
 613                }
 614        }
 615        return error;
 616}
 617
 618/*
 619 * __mm_populate - populate and/or mlock pages within a range of address space.
 620 *
 621 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
 622 * flags. VMAs must be already marked with the desired vm_flags, and
 623 * mmap_sem must not be held.
 624 */
 625int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 626{
 627        struct mm_struct *mm = current->mm;
 628        unsigned long end, nstart, nend;
 629        struct vm_area_struct *vma = NULL;
 630        int locked = 0;
 631        long ret = 0;
 632
 633        VM_BUG_ON(start & ~PAGE_MASK);
 634        VM_BUG_ON(len != PAGE_ALIGN(len));
 635        end = start + len;
 636
 637        for (nstart = start; nstart < end; nstart = nend) {
 638                /*
 639                 * We want to fault in pages for [nstart; end) address range.
 640                 * Find first corresponding VMA.
 641                 */
 642                if (!locked) {
 643                        locked = 1;
 644                        down_read(&mm->mmap_sem);
 645                        vma = find_vma(mm, nstart);
 646                } else if (nstart >= vma->vm_end)
 647                        vma = vma->vm_next;
 648                if (!vma || vma->vm_start >= end)
 649                        break;
 650                /*
 651                 * Set [nstart; nend) to intersection of desired address
 652                 * range with the first VMA. Also, skip undesirable VMA types.
 653                 */
 654                nend = min(end, vma->vm_end);
 655                if (vma->vm_flags & (VM_IO | VM_PFNMAP))
 656                        continue;
 657                if (nstart < vma->vm_start)
 658                        nstart = vma->vm_start;
 659                /*
 660                 * Now fault in a range of pages. __mlock_vma_pages_range()
 661                 * double checks the vma flags, so that it won't mlock pages
 662                 * if the vma was already munlocked.
 663                 */
 664                ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
 665                if (ret < 0) {
 666                        if (ignore_errors) {
 667                                ret = 0;
 668                                continue;       /* continue at next VMA */
 669                        }
 670                        ret = __mlock_posix_error_return(ret);
 671                        break;
 672                }
 673                nend = nstart + ret * PAGE_SIZE;
 674                ret = 0;
 675        }
 676        if (locked)
 677                up_read(&mm->mmap_sem);
 678        return ret;     /* 0 or negative error code */
 679}
 680
 681SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 682{
 683        unsigned long locked;
 684        unsigned long lock_limit;
 685        int error = -ENOMEM;
 686
 687        if (!can_do_mlock())
 688                return -EPERM;
 689
 690        lru_add_drain_all();    /* flush pagevec */
 691
 692        down_write(&current->mm->mmap_sem);
 693        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 694        start &= PAGE_MASK;
 695
 696        locked = len >> PAGE_SHIFT;
 697        locked += current->mm->locked_vm;
 698
 699        lock_limit = rlimit(RLIMIT_MEMLOCK);
 700        lock_limit >>= PAGE_SHIFT;
 701
 702        /* check against resource limits */
 703        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 704                error = do_mlock(start, len, 1);
 705        up_write(&current->mm->mmap_sem);
 706        if (!error)
 707                error = __mm_populate(start, len, 0);
 708        return error;
 709}
 710
 711SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 712{
 713        int ret;
 714
 715        down_write(&current->mm->mmap_sem);
 716        len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
 717        start &= PAGE_MASK;
 718        ret = do_mlock(start, len, 0);
 719        up_write(&current->mm->mmap_sem);
 720        return ret;
 721}
 722
 723static int do_mlockall(int flags)
 724{
 725        struct vm_area_struct * vma, * prev = NULL;
 726
 727        if (flags & MCL_FUTURE)
 728                current->mm->def_flags |= VM_LOCKED;
 729        else
 730                current->mm->def_flags &= ~VM_LOCKED;
 731        if (flags == MCL_FUTURE)
 732                goto out;
 733
 734        for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 735                vm_flags_t newflags;
 736
 737                newflags = vma->vm_flags & ~VM_LOCKED;
 738                if (flags & MCL_CURRENT)
 739                        newflags |= VM_LOCKED;
 740
 741                /* Ignore errors */
 742                mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 743                cond_resched();
 744        }
 745out:
 746        return 0;
 747}
 748
 749SYSCALL_DEFINE1(mlockall, int, flags)
 750{
 751        unsigned long lock_limit;
 752        int ret = -EINVAL;
 753
 754        if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
 755                goto out;
 756
 757        ret = -EPERM;
 758        if (!can_do_mlock())
 759                goto out;
 760
 761        if (flags & MCL_CURRENT)
 762                lru_add_drain_all();    /* flush pagevec */
 763
 764        down_write(&current->mm->mmap_sem);
 765
 766        lock_limit = rlimit(RLIMIT_MEMLOCK);
 767        lock_limit >>= PAGE_SHIFT;
 768
 769        ret = -ENOMEM;
 770        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 771            capable(CAP_IPC_LOCK))
 772                ret = do_mlockall(flags);
 773        up_write(&current->mm->mmap_sem);
 774        if (!ret && (flags & MCL_CURRENT))
 775                mm_populate(0, TASK_SIZE);
 776out:
 777        return ret;
 778}
 779
 780SYSCALL_DEFINE0(munlockall)
 781{
 782        int ret;
 783
 784        down_write(&current->mm->mmap_sem);
 785        ret = do_mlockall(0);
 786        up_write(&current->mm->mmap_sem);
 787        return ret;
 788}
 789
 790/*
 791 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 792 * shm segments) get accounted against the user_struct instead.
 793 */
 794static DEFINE_SPINLOCK(shmlock_user_lock);
 795
 796int user_shm_lock(size_t size, struct user_struct *user)
 797{
 798        unsigned long lock_limit, locked;
 799        int allowed = 0;
 800
 801        locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 802        lock_limit = rlimit(RLIMIT_MEMLOCK);
 803        if (lock_limit == RLIM_INFINITY)
 804                allowed = 1;
 805        lock_limit >>= PAGE_SHIFT;
 806        spin_lock(&shmlock_user_lock);
 807        if (!allowed &&
 808            locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 809                goto out;
 810        get_uid(user);
 811        user->locked_shm += locked;
 812        allowed = 1;
 813out:
 814        spin_unlock(&shmlock_user_lock);
 815        return allowed;
 816}
 817
 818void user_shm_unlock(size_t size, struct user_struct *user)
 819{
 820        spin_lock(&shmlock_user_lock);
 821        user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 822        spin_unlock(&shmlock_user_lock);
 823        free_uid(user);
 824}
 825
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