linux/mm/mlock.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *      linux/mm/mlock.c
   4 *
   5 *  (C) Copyright 1995 Linus Torvalds
   6 *  (C) Copyright 2002 Christoph Hellwig
   7 */
   8
   9#include <linux/capability.h>
  10#include <linux/mman.h>
  11#include <linux/mm.h>
  12#include <linux/sched/user.h>
  13#include <linux/swap.h>
  14#include <linux/swapops.h>
  15#include <linux/pagemap.h>
  16#include <linux/pagevec.h>
  17#include <linux/mempolicy.h>
  18#include <linux/syscalls.h>
  19#include <linux/sched.h>
  20#include <linux/export.h>
  21#include <linux/rmap.h>
  22#include <linux/mmzone.h>
  23#include <linux/hugetlb.h>
  24#include <linux/memcontrol.h>
  25#include <linux/mm_inline.h>
  26
  27#include "internal.h"
  28
  29bool can_do_mlock(void)
  30{
  31        if (rlimit(RLIMIT_MEMLOCK) != 0)
  32                return true;
  33        if (capable(CAP_IPC_LOCK))
  34                return true;
  35        return false;
  36}
  37EXPORT_SYMBOL(can_do_mlock);
  38
  39/*
  40 * Mlocked pages are marked with PageMlocked() flag for efficient testing
  41 * in vmscan and, possibly, the fault path; and to support semi-accurate
  42 * statistics.
  43 *
  44 * An mlocked page [PageMlocked(page)] is unevictable.  As such, it will
  45 * be placed on the LRU "unevictable" list, rather than the [in]active lists.
  46 * The unevictable list is an LRU sibling list to the [in]active lists.
  47 * PageUnevictable is set to indicate the unevictable state.
  48 *
  49 * When lazy mlocking via vmscan, it is important to ensure that the
  50 * vma's VM_LOCKED status is not concurrently being modified, otherwise we
  51 * may have mlocked a page that is being munlocked. So lazy mlock must take
  52 * the mmap_sem for read, and verify that the vma really is locked
  53 * (see mm/rmap.c).
  54 */
  55
  56/*
  57 *  LRU accounting for clear_page_mlock()
  58 */
  59void clear_page_mlock(struct page *page)
  60{
  61        if (!TestClearPageMlocked(page))
  62                return;
  63
  64        mod_zone_page_state(page_zone(page), NR_MLOCK,
  65                            -hpage_nr_pages(page));
  66        count_vm_event(UNEVICTABLE_PGCLEARED);
  67        /*
  68         * The previous TestClearPageMlocked() corresponds to the smp_mb()
  69         * in __pagevec_lru_add_fn().
  70         *
  71         * See __pagevec_lru_add_fn for more explanation.
  72         */
  73        if (!isolate_lru_page(page)) {
  74                putback_lru_page(page);
  75        } else {
  76                /*
  77                 * We lost the race. the page already moved to evictable list.
  78                 */
  79                if (PageUnevictable(page))
  80                        count_vm_event(UNEVICTABLE_PGSTRANDED);
  81        }
  82}
  83
  84/*
  85 * Mark page as mlocked if not already.
  86 * If page on LRU, isolate and putback to move to unevictable list.
  87 */
  88void mlock_vma_page(struct page *page)
  89{
  90        /* Serialize with page migration */
  91        BUG_ON(!PageLocked(page));
  92
  93        VM_BUG_ON_PAGE(PageTail(page), page);
  94        VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
  95
  96        if (!TestSetPageMlocked(page)) {
  97                mod_zone_page_state(page_zone(page), NR_MLOCK,
  98                                    hpage_nr_pages(page));
  99                count_vm_event(UNEVICTABLE_PGMLOCKED);
 100                if (!isolate_lru_page(page))
 101                        putback_lru_page(page);
 102        }
 103}
 104
 105/*
 106 * Isolate a page from LRU with optional get_page() pin.
 107 * Assumes lru_lock already held and page already pinned.
 108 */
 109static bool __munlock_isolate_lru_page(struct page *page, bool getpage)
 110{
 111        if (PageLRU(page)) {
 112                struct lruvec *lruvec;
 113
 114                lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
 115                if (getpage)
 116                        get_page(page);
 117                ClearPageLRU(page);
 118                del_page_from_lru_list(page, lruvec, page_lru(page));
 119                return true;
 120        }
 121
 122        return false;
 123}
 124
 125/*
 126 * Finish munlock after successful page isolation
 127 *
 128 * Page must be locked. This is a wrapper for try_to_munlock()
 129 * and putback_lru_page() with munlock accounting.
 130 */
 131static void __munlock_isolated_page(struct page *page)
 132{
 133        /*
 134         * Optimization: if the page was mapped just once, that's our mapping
 135         * and we don't need to check all the other vmas.
 136         */
 137        if (page_mapcount(page) > 1)
 138                try_to_munlock(page);
 139
 140        /* Did try_to_unlock() succeed or punt? */
 141        if (!PageMlocked(page))
 142                count_vm_event(UNEVICTABLE_PGMUNLOCKED);
 143
 144        putback_lru_page(page);
 145}
 146
 147/*
 148 * Accounting for page isolation fail during munlock
 149 *
 150 * Performs accounting when page isolation fails in munlock. There is nothing
 151 * else to do because it means some other task has already removed the page
 152 * from the LRU. putback_lru_page() will take care of removing the page from
 153 * the unevictable list, if necessary. vmscan [page_referenced()] will move
 154 * the page back to the unevictable list if some other vma has it mlocked.
 155 */
 156static void __munlock_isolation_failed(struct page *page)
 157{
 158        if (PageUnevictable(page))
 159                __count_vm_event(UNEVICTABLE_PGSTRANDED);
 160        else
 161                __count_vm_event(UNEVICTABLE_PGMUNLOCKED);
 162}
 163
 164/**
 165 * munlock_vma_page - munlock a vma page
 166 * @page: page to be unlocked, either a normal page or THP page head
 167 *
 168 * returns the size of the page as a page mask (0 for normal page,
 169 *         HPAGE_PMD_NR - 1 for THP head page)
 170 *
 171 * called from munlock()/munmap() path with page supposedly on the LRU.
 172 * When we munlock a page, because the vma where we found the page is being
 173 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
 174 * page locked so that we can leave it on the unevictable lru list and not
 175 * bother vmscan with it.  However, to walk the page's rmap list in
 176 * try_to_munlock() we must isolate the page from the LRU.  If some other
 177 * task has removed the page from the LRU, we won't be able to do that.
 178 * So we clear the PageMlocked as we might not get another chance.  If we
 179 * can't isolate the page, we leave it for putback_lru_page() and vmscan
 180 * [page_referenced()/try_to_unmap()] to deal with.
 181 */
 182unsigned int munlock_vma_page(struct page *page)
 183{
 184        int nr_pages;
 185        pg_data_t *pgdat = page_pgdat(page);
 186
 187        /* For try_to_munlock() and to serialize with page migration */
 188        BUG_ON(!PageLocked(page));
 189
 190        VM_BUG_ON_PAGE(PageTail(page), page);
 191
 192        /*
 193         * Serialize with any parallel __split_huge_page_refcount() which
 194         * might otherwise copy PageMlocked to part of the tail pages before
 195         * we clear it in the head page. It also stabilizes hpage_nr_pages().
 196         */
 197        spin_lock_irq(&pgdat->lru_lock);
 198
 199        if (!TestClearPageMlocked(page)) {
 200                /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
 201                nr_pages = 1;
 202                goto unlock_out;
 203        }
 204
 205        nr_pages = hpage_nr_pages(page);
 206        __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
 207
 208        if (__munlock_isolate_lru_page(page, true)) {
 209                spin_unlock_irq(&pgdat->lru_lock);
 210                __munlock_isolated_page(page);
 211                goto out;
 212        }
 213        __munlock_isolation_failed(page);
 214
 215unlock_out:
 216        spin_unlock_irq(&pgdat->lru_lock);
 217
 218out:
 219        return nr_pages - 1;
 220}
 221
 222/*
 223 * convert get_user_pages() return value to posix mlock() error
 224 */
 225static int __mlock_posix_error_return(long retval)
 226{
 227        if (retval == -EFAULT)
 228                retval = -ENOMEM;
 229        else if (retval == -ENOMEM)
 230                retval = -EAGAIN;
 231        return retval;
 232}
 233
 234/*
 235 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
 236 *
 237 * The fast path is available only for evictable pages with single mapping.
 238 * Then we can bypass the per-cpu pvec and get better performance.
 239 * when mapcount > 1 we need try_to_munlock() which can fail.
 240 * when !page_evictable(), we need the full redo logic of putback_lru_page to
 241 * avoid leaving evictable page in unevictable list.
 242 *
 243 * In case of success, @page is added to @pvec and @pgrescued is incremented
 244 * in case that the page was previously unevictable. @page is also unlocked.
 245 */
 246static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
 247                int *pgrescued)
 248{
 249        VM_BUG_ON_PAGE(PageLRU(page), page);
 250        VM_BUG_ON_PAGE(!PageLocked(page), page);
 251
 252        if (page_mapcount(page) <= 1 && page_evictable(page)) {
 253                pagevec_add(pvec, page);
 254                if (TestClearPageUnevictable(page))
 255                        (*pgrescued)++;
 256                unlock_page(page);
 257                return true;
 258        }
 259
 260        return false;
 261}
 262
 263/*
 264 * Putback multiple evictable pages to the LRU
 265 *
 266 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
 267 * the pages might have meanwhile become unevictable but that is OK.
 268 */
 269static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
 270{
 271        count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
 272        /*
 273         *__pagevec_lru_add() calls release_pages() so we don't call
 274         * put_page() explicitly
 275         */
 276        __pagevec_lru_add(pvec);
 277        count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
 278}
 279
 280/*
 281 * Munlock a batch of pages from the same zone
 282 *
 283 * The work is split to two main phases. First phase clears the Mlocked flag
 284 * and attempts to isolate the pages, all under a single zone lru lock.
 285 * The second phase finishes the munlock only for pages where isolation
 286 * succeeded.
 287 *
 288 * Note that the pagevec may be modified during the process.
 289 */
 290static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 291{
 292        int i;
 293        int nr = pagevec_count(pvec);
 294        int delta_munlocked = -nr;
 295        struct pagevec pvec_putback;
 296        int pgrescued = 0;
 297
 298        pagevec_init(&pvec_putback);
 299
 300        /* Phase 1: page isolation */
 301        spin_lock_irq(&zone->zone_pgdat->lru_lock);
 302        for (i = 0; i < nr; i++) {
 303                struct page *page = pvec->pages[i];
 304
 305                if (TestClearPageMlocked(page)) {
 306                        /*
 307                         * We already have pin from follow_page_mask()
 308                         * so we can spare the get_page() here.
 309                         */
 310                        if (__munlock_isolate_lru_page(page, false))
 311                                continue;
 312                        else
 313                                __munlock_isolation_failed(page);
 314                } else {
 315                        delta_munlocked++;
 316                }
 317
 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. We cannot do it under lru_lock however. If it's
 322                 * the last pin, __page_cache_release() would deadlock.
 323                 */
 324                pagevec_add(&pvec_putback, pvec->pages[i]);
 325                pvec->pages[i] = NULL;
 326        }
 327        __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
 328        spin_unlock_irq(&zone->zone_pgdat->lru_lock);
 329
 330        /* Now we can release pins of pages that we are not munlocking */
 331        pagevec_release(&pvec_putback);
 332
 333        /* Phase 2: page munlock */
 334        for (i = 0; i < nr; i++) {
 335                struct page *page = pvec->pages[i];
 336
 337                if (page) {
 338                        lock_page(page);
 339                        if (!__putback_lru_fast_prepare(page, &pvec_putback,
 340                                        &pgrescued)) {
 341                                /*
 342                                 * Slow path. We don't want to lose the last
 343                                 * pin before unlock_page()
 344                                 */
 345                                get_page(page); /* for putback_lru_page() */
 346                                __munlock_isolated_page(page);
 347                                unlock_page(page);
 348                                put_page(page); /* from follow_page_mask() */
 349                        }
 350                }
 351        }
 352
 353        /*
 354         * Phase 3: page putback for pages that qualified for the fast path
 355         * This will also call put_page() to return pin from follow_page_mask()
 356         */
 357        if (pagevec_count(&pvec_putback))
 358                __putback_lru_fast(&pvec_putback, pgrescued);
 359}
 360
 361/*
 362 * Fill up pagevec for __munlock_pagevec using pte walk
 363 *
 364 * The function expects that the struct page corresponding to @start address is
 365 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
 366 *
 367 * The rest of @pvec is filled by subsequent pages within the same pmd and same
 368 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
 369 * pages also get pinned.
 370 *
 371 * Returns the address of the next page that should be scanned. This equals
 372 * @start + PAGE_SIZE when no page could be added by the pte walk.
 373 */
 374static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
 375                        struct vm_area_struct *vma, struct zone *zone,
 376                        unsigned long start, unsigned long end)
 377{
 378        pte_t *pte;
 379        spinlock_t *ptl;
 380
 381        /*
 382         * Initialize pte walk starting at the already pinned page where we
 383         * are sure that there is a pte, as it was pinned under the same
 384         * mmap_sem write op.
 385         */
 386        pte = get_locked_pte(vma->vm_mm, start, &ptl);
 387        /* Make sure we do not cross the page table boundary */
 388        end = pgd_addr_end(start, end);
 389        end = p4d_addr_end(start, end);
 390        end = pud_addr_end(start, end);
 391        end = pmd_addr_end(start, end);
 392
 393        /* The page next to the pinned page is the first we will try to get */
 394        start += PAGE_SIZE;
 395        while (start < end) {
 396                struct page *page = NULL;
 397                pte++;
 398                if (pte_present(*pte))
 399                        page = vm_normal_page(vma, start, *pte);
 400                /*
 401                 * Break if page could not be obtained or the page's node+zone does not
 402                 * match
 403                 */
 404                if (!page || page_zone(page) != zone)
 405                        break;
 406
 407                /*
 408                 * Do not use pagevec for PTE-mapped THP,
 409                 * munlock_vma_pages_range() will handle them.
 410                 */
 411                if (PageTransCompound(page))
 412                        break;
 413
 414                get_page(page);
 415                /*
 416                 * Increase the address that will be returned *before* the
 417                 * eventual break due to pvec becoming full by adding the page
 418                 */
 419                start += PAGE_SIZE;
 420                if (pagevec_add(pvec, page) == 0)
 421                        break;
 422        }
 423        pte_unmap_unlock(pte, ptl);
 424        return start;
 425}
 426
 427/*
 428 * munlock_vma_pages_range() - munlock all pages in the vma range.'
 429 * @vma - vma containing range to be munlock()ed.
 430 * @start - start address in @vma of the range
 431 * @end - end of range in @vma.
 432 *
 433 *  For mremap(), munmap() and exit().
 434 *
 435 * Called with @vma VM_LOCKED.
 436 *
 437 * Returns with VM_LOCKED cleared.  Callers must be prepared to
 438 * deal with this.
 439 *
 440 * We don't save and restore VM_LOCKED here because pages are
 441 * still on lru.  In unmap path, pages might be scanned by reclaim
 442 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
 443 * free them.  This will result in freeing mlocked pages.
 444 */
 445void munlock_vma_pages_range(struct vm_area_struct *vma,
 446                             unsigned long start, unsigned long end)
 447{
 448        vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
 449
 450        while (start < end) {
 451                struct page *page;
 452                unsigned int page_mask = 0;
 453                unsigned long page_increm;
 454                struct pagevec pvec;
 455                struct zone *zone;
 456
 457                pagevec_init(&pvec);
 458                /*
 459                 * Although FOLL_DUMP is intended for get_dump_page(),
 460                 * it just so happens that its special treatment of the
 461                 * ZERO_PAGE (returning an error instead of doing get_page)
 462                 * suits munlock very well (and if somehow an abnormal page
 463                 * has sneaked into the range, we won't oops here: great).
 464                 */
 465                page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
 466
 467                if (page && !IS_ERR(page)) {
 468                        if (PageTransTail(page)) {
 469                                VM_BUG_ON_PAGE(PageMlocked(page), page);
 470                                put_page(page); /* follow_page_mask() */
 471                        } else if (PageTransHuge(page)) {
 472                                lock_page(page);
 473                                /*
 474                                 * Any THP page found by follow_page_mask() may
 475                                 * have gotten split before reaching
 476                                 * munlock_vma_page(), so we need to compute
 477                                 * the page_mask here instead.
 478                                 */
 479                                page_mask = munlock_vma_page(page);
 480                                unlock_page(page);
 481                                put_page(page); /* follow_page_mask() */
 482                        } else {
 483                                /*
 484                                 * Non-huge pages are handled in batches via
 485                                 * pagevec. The pin from follow_page_mask()
 486                                 * prevents them from collapsing by THP.
 487                                 */
 488                                pagevec_add(&pvec, page);
 489                                zone = page_zone(page);
 490
 491                                /*
 492                                 * Try to fill the rest of pagevec using fast
 493                                 * pte walk. This will also update start to
 494                                 * the next page to process. Then munlock the
 495                                 * pagevec.
 496                                 */
 497                                start = __munlock_pagevec_fill(&pvec, vma,
 498                                                zone, start, end);
 499                                __munlock_pagevec(&pvec, zone);
 500                                goto next;
 501                        }
 502                }
 503                page_increm = 1 + page_mask;
 504                start += page_increm * PAGE_SIZE;
 505next:
 506                cond_resched();
 507        }
 508}
 509
 510/*
 511 * mlock_fixup  - handle mlock[all]/munlock[all] requests.
 512 *
 513 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
 514 * munlock is a no-op.  However, for some special vmas, we go ahead and
 515 * populate the ptes.
 516 *
 517 * For vmas that pass the filters, merge/split as appropriate.
 518 */
 519static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 520        unsigned long start, unsigned long end, vm_flags_t newflags)
 521{
 522        struct mm_struct *mm = vma->vm_mm;
 523        pgoff_t pgoff;
 524        int nr_pages;
 525        int ret = 0;
 526        int lock = !!(newflags & VM_LOCKED);
 527        vm_flags_t old_flags = vma->vm_flags;
 528
 529        if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
 530            is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
 531            vma_is_dax(vma))
 532                /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
 533                goto out;
 534
 535        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 536        *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
 537                          vma->vm_file, pgoff, vma_policy(vma),
 538                          vma->vm_userfaultfd_ctx);
 539        if (*prev) {
 540                vma = *prev;
 541                goto success;
 542        }
 543
 544        if (start != vma->vm_start) {
 545                ret = split_vma(mm, vma, start, 1);
 546                if (ret)
 547                        goto out;
 548        }
 549
 550        if (end != vma->vm_end) {
 551                ret = split_vma(mm, vma, end, 0);
 552                if (ret)
 553                        goto out;
 554        }
 555
 556success:
 557        /*
 558         * Keep track of amount of locked VM.
 559         */
 560        nr_pages = (end - start) >> PAGE_SHIFT;
 561        if (!lock)
 562                nr_pages = -nr_pages;
 563        else if (old_flags & VM_LOCKED)
 564                nr_pages = 0;
 565        mm->locked_vm += nr_pages;
 566
 567        /*
 568         * vm_flags is protected by the mmap_sem held in write mode.
 569         * It's okay if try_to_unmap_one unmaps a page just after we
 570         * set VM_LOCKED, populate_vma_page_range will bring it back.
 571         */
 572
 573        if (lock)
 574                vma->vm_flags = newflags;
 575        else
 576                munlock_vma_pages_range(vma, start, end);
 577
 578out:
 579        *prev = vma;
 580        return ret;
 581}
 582
 583static int apply_vma_lock_flags(unsigned long start, size_t len,
 584                                vm_flags_t flags)
 585{
 586        unsigned long nstart, end, tmp;
 587        struct vm_area_struct * vma, * prev;
 588        int error;
 589
 590        VM_BUG_ON(offset_in_page(start));
 591        VM_BUG_ON(len != PAGE_ALIGN(len));
 592        end = start + len;
 593        if (end < start)
 594                return -EINVAL;
 595        if (end == start)
 596                return 0;
 597        vma = find_vma(current->mm, start);
 598        if (!vma || vma->vm_start > start)
 599                return -ENOMEM;
 600
 601        prev = vma->vm_prev;
 602        if (start > vma->vm_start)
 603                prev = vma;
 604
 605        for (nstart = start ; ; ) {
 606                vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
 607
 608                newflags |= flags;
 609
 610                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 611                tmp = vma->vm_end;
 612                if (tmp > end)
 613                        tmp = end;
 614                error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 615                if (error)
 616                        break;
 617                nstart = tmp;
 618                if (nstart < prev->vm_end)
 619                        nstart = prev->vm_end;
 620                if (nstart >= end)
 621                        break;
 622
 623                vma = prev->vm_next;
 624                if (!vma || vma->vm_start != nstart) {
 625                        error = -ENOMEM;
 626                        break;
 627                }
 628        }
 629        return error;
 630}
 631
 632/*
 633 * Go through vma areas and sum size of mlocked
 634 * vma pages, as return value.
 635 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
 636 * is also counted.
 637 * Return value: previously mlocked page counts
 638 */
 639static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
 640                unsigned long start, size_t len)
 641{
 642        struct vm_area_struct *vma;
 643        unsigned long count = 0;
 644
 645        if (mm == NULL)
 646                mm = current->mm;
 647
 648        vma = find_vma(mm, start);
 649        if (vma == NULL)
 650                vma = mm->mmap;
 651
 652        for (; vma ; vma = vma->vm_next) {
 653                if (start >= vma->vm_end)
 654                        continue;
 655                if (start + len <=  vma->vm_start)
 656                        break;
 657                if (vma->vm_flags & VM_LOCKED) {
 658                        if (start > vma->vm_start)
 659                                count -= (start - vma->vm_start);
 660                        if (start + len < vma->vm_end) {
 661                                count += start + len - vma->vm_start;
 662                                break;
 663                        }
 664                        count += vma->vm_end - vma->vm_start;
 665                }
 666        }
 667
 668        return count >> PAGE_SHIFT;
 669}
 670
 671static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
 672{
 673        unsigned long locked;
 674        unsigned long lock_limit;
 675        int error = -ENOMEM;
 676
 677        start = untagged_addr(start);
 678
 679        if (!can_do_mlock())
 680                return -EPERM;
 681
 682        len = PAGE_ALIGN(len + (offset_in_page(start)));
 683        start &= PAGE_MASK;
 684
 685        lock_limit = rlimit(RLIMIT_MEMLOCK);
 686        lock_limit >>= PAGE_SHIFT;
 687        locked = len >> PAGE_SHIFT;
 688
 689        if (down_write_killable(&current->mm->mmap_sem))
 690                return -EINTR;
 691
 692        locked += current->mm->locked_vm;
 693        if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
 694                /*
 695                 * It is possible that the regions requested intersect with
 696                 * previously mlocked areas, that part area in "mm->locked_vm"
 697                 * should not be counted to new mlock increment count. So check
 698                 * and adjust locked count if necessary.
 699                 */
 700                locked -= count_mm_mlocked_page_nr(current->mm,
 701                                start, len);
 702        }
 703
 704        /* check against resource limits */
 705        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 706                error = apply_vma_lock_flags(start, len, flags);
 707
 708        up_write(&current->mm->mmap_sem);
 709        if (error)
 710                return error;
 711
 712        error = __mm_populate(start, len, 0);
 713        if (error)
 714                return __mlock_posix_error_return(error);
 715        return 0;
 716}
 717
 718SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 719{
 720        return do_mlock(start, len, VM_LOCKED);
 721}
 722
 723SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
 724{
 725        vm_flags_t vm_flags = VM_LOCKED;
 726
 727        if (flags & ~MLOCK_ONFAULT)
 728                return -EINVAL;
 729
 730        if (flags & MLOCK_ONFAULT)
 731                vm_flags |= VM_LOCKONFAULT;
 732
 733        return do_mlock(start, len, vm_flags);
 734}
 735
 736SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 737{
 738        int ret;
 739
 740        start = untagged_addr(start);
 741
 742        len = PAGE_ALIGN(len + (offset_in_page(start)));
 743        start &= PAGE_MASK;
 744
 745        if (down_write_killable(&current->mm->mmap_sem))
 746                return -EINTR;
 747        ret = apply_vma_lock_flags(start, len, 0);
 748        up_write(&current->mm->mmap_sem);
 749
 750        return ret;
 751}
 752
 753/*
 754 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
 755 * and translate into the appropriate modifications to mm->def_flags and/or the
 756 * flags for all current VMAs.
 757 *
 758 * There are a couple of subtleties with this.  If mlockall() is called multiple
 759 * times with different flags, the values do not necessarily stack.  If mlockall
 760 * is called once including the MCL_FUTURE flag and then a second time without
 761 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
 762 */
 763static int apply_mlockall_flags(int flags)
 764{
 765        struct vm_area_struct * vma, * prev = NULL;
 766        vm_flags_t to_add = 0;
 767
 768        current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
 769        if (flags & MCL_FUTURE) {
 770                current->mm->def_flags |= VM_LOCKED;
 771
 772                if (flags & MCL_ONFAULT)
 773                        current->mm->def_flags |= VM_LOCKONFAULT;
 774
 775                if (!(flags & MCL_CURRENT))
 776                        goto out;
 777        }
 778
 779        if (flags & MCL_CURRENT) {
 780                to_add |= VM_LOCKED;
 781                if (flags & MCL_ONFAULT)
 782                        to_add |= VM_LOCKONFAULT;
 783        }
 784
 785        for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 786                vm_flags_t newflags;
 787
 788                newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
 789                newflags |= to_add;
 790
 791                /* Ignore errors */
 792                mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 793                cond_resched();
 794        }
 795out:
 796        return 0;
 797}
 798
 799SYSCALL_DEFINE1(mlockall, int, flags)
 800{
 801        unsigned long lock_limit;
 802        int ret;
 803
 804        if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
 805            flags == MCL_ONFAULT)
 806                return -EINVAL;
 807
 808        if (!can_do_mlock())
 809                return -EPERM;
 810
 811        lock_limit = rlimit(RLIMIT_MEMLOCK);
 812        lock_limit >>= PAGE_SHIFT;
 813
 814        if (down_write_killable(&current->mm->mmap_sem))
 815                return -EINTR;
 816
 817        ret = -ENOMEM;
 818        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 819            capable(CAP_IPC_LOCK))
 820                ret = apply_mlockall_flags(flags);
 821        up_write(&current->mm->mmap_sem);
 822        if (!ret && (flags & MCL_CURRENT))
 823                mm_populate(0, TASK_SIZE);
 824
 825        return ret;
 826}
 827
 828SYSCALL_DEFINE0(munlockall)
 829{
 830        int ret;
 831
 832        if (down_write_killable(&current->mm->mmap_sem))
 833                return -EINTR;
 834        ret = apply_mlockall_flags(0);
 835        up_write(&current->mm->mmap_sem);
 836        return ret;
 837}
 838
 839/*
 840 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 841 * shm segments) get accounted against the user_struct instead.
 842 */
 843static DEFINE_SPINLOCK(shmlock_user_lock);
 844
 845int user_shm_lock(size_t size, struct user_struct *user)
 846{
 847        unsigned long lock_limit, locked;
 848        int allowed = 0;
 849
 850        locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 851        lock_limit = rlimit(RLIMIT_MEMLOCK);
 852        if (lock_limit == RLIM_INFINITY)
 853                allowed = 1;
 854        lock_limit >>= PAGE_SHIFT;
 855        spin_lock(&shmlock_user_lock);
 856        if (!allowed &&
 857            locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 858                goto out;
 859        get_uid(user);
 860        user->locked_shm += locked;
 861        allowed = 1;
 862out:
 863        spin_unlock(&shmlock_user_lock);
 864        return allowed;
 865}
 866
 867void user_shm_unlock(size_t size, struct user_struct *user)
 868{
 869        spin_lock(&shmlock_user_lock);
 870        user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 871        spin_unlock(&shmlock_user_lock);
 872        free_uid(user);
 873}
 874