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_lock 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        int nr_pages;
  62
  63        if (!TestClearPageMlocked(page))
  64                return;
  65
  66        nr_pages = thp_nr_pages(page);
  67        mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
  68        count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
  69        /*
  70         * The previous TestClearPageMlocked() corresponds to the smp_mb()
  71         * in __pagevec_lru_add_fn().
  72         *
  73         * See __pagevec_lru_add_fn for more explanation.
  74         */
  75        if (!isolate_lru_page(page)) {
  76                putback_lru_page(page);
  77        } else {
  78                /*
  79                 * We lost the race. the page already moved to evictable list.
  80                 */
  81                if (PageUnevictable(page))
  82                        count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
  83        }
  84}
  85
  86/*
  87 * Mark page as mlocked if not already.
  88 * If page on LRU, isolate and putback to move to unevictable list.
  89 */
  90void mlock_vma_page(struct page *page)
  91{
  92        /* Serialize with page migration */
  93        BUG_ON(!PageLocked(page));
  94
  95        VM_BUG_ON_PAGE(PageTail(page), page);
  96        VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
  97
  98        if (!TestSetPageMlocked(page)) {
  99                int nr_pages = thp_nr_pages(page);
 100
 101                mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
 102                count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
 103                if (!isolate_lru_page(page))
 104                        putback_lru_page(page);
 105        }
 106}
 107
 108/*
 109 * Finish munlock after successful page isolation
 110 *
 111 * Page must be locked. This is a wrapper for try_to_munlock()
 112 * and putback_lru_page() with munlock accounting.
 113 */
 114static void __munlock_isolated_page(struct page *page)
 115{
 116        /*
 117         * Optimization: if the page was mapped just once, that's our mapping
 118         * and we don't need to check all the other vmas.
 119         */
 120        if (page_mapcount(page) > 1)
 121                try_to_munlock(page);
 122
 123        /* Did try_to_unlock() succeed or punt? */
 124        if (!PageMlocked(page))
 125                count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page));
 126
 127        putback_lru_page(page);
 128}
 129
 130/*
 131 * Accounting for page isolation fail during munlock
 132 *
 133 * Performs accounting when page isolation fails in munlock. There is nothing
 134 * else to do because it means some other task has already removed the page
 135 * from the LRU. putback_lru_page() will take care of removing the page from
 136 * the unevictable list, if necessary. vmscan [page_referenced()] will move
 137 * the page back to the unevictable list if some other vma has it mlocked.
 138 */
 139static void __munlock_isolation_failed(struct page *page)
 140{
 141        int nr_pages = thp_nr_pages(page);
 142
 143        if (PageUnevictable(page))
 144                __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
 145        else
 146                __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
 147}
 148
 149/**
 150 * munlock_vma_page - munlock a vma page
 151 * @page: page to be unlocked, either a normal page or THP page head
 152 *
 153 * returns the size of the page as a page mask (0 for normal page,
 154 *         HPAGE_PMD_NR - 1 for THP head page)
 155 *
 156 * called from munlock()/munmap() path with page supposedly on the LRU.
 157 * When we munlock a page, because the vma where we found the page is being
 158 * munlock()ed or munmap()ed, we want to check whether other vmas hold the
 159 * page locked so that we can leave it on the unevictable lru list and not
 160 * bother vmscan with it.  However, to walk the page's rmap list in
 161 * try_to_munlock() we must isolate the page from the LRU.  If some other
 162 * task has removed the page from the LRU, we won't be able to do that.
 163 * So we clear the PageMlocked as we might not get another chance.  If we
 164 * can't isolate the page, we leave it for putback_lru_page() and vmscan
 165 * [page_referenced()/try_to_unmap()] to deal with.
 166 */
 167unsigned int munlock_vma_page(struct page *page)
 168{
 169        int nr_pages;
 170
 171        /* For try_to_munlock() and to serialize with page migration */
 172        BUG_ON(!PageLocked(page));
 173        VM_BUG_ON_PAGE(PageTail(page), page);
 174
 175        if (!TestClearPageMlocked(page)) {
 176                /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
 177                return 0;
 178        }
 179
 180        nr_pages = thp_nr_pages(page);
 181        mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
 182
 183        if (!isolate_lru_page(page))
 184                __munlock_isolated_page(page);
 185        else
 186                __munlock_isolation_failed(page);
 187
 188        return nr_pages - 1;
 189}
 190
 191/*
 192 * convert get_user_pages() return value to posix mlock() error
 193 */
 194static int __mlock_posix_error_return(long retval)
 195{
 196        if (retval == -EFAULT)
 197                retval = -ENOMEM;
 198        else if (retval == -ENOMEM)
 199                retval = -EAGAIN;
 200        return retval;
 201}
 202
 203/*
 204 * Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
 205 *
 206 * The fast path is available only for evictable pages with single mapping.
 207 * Then we can bypass the per-cpu pvec and get better performance.
 208 * when mapcount > 1 we need try_to_munlock() which can fail.
 209 * when !page_evictable(), we need the full redo logic of putback_lru_page to
 210 * avoid leaving evictable page in unevictable list.
 211 *
 212 * In case of success, @page is added to @pvec and @pgrescued is incremented
 213 * in case that the page was previously unevictable. @page is also unlocked.
 214 */
 215static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
 216                int *pgrescued)
 217{
 218        VM_BUG_ON_PAGE(PageLRU(page), page);
 219        VM_BUG_ON_PAGE(!PageLocked(page), page);
 220
 221        if (page_mapcount(page) <= 1 && page_evictable(page)) {
 222                pagevec_add(pvec, page);
 223                if (TestClearPageUnevictable(page))
 224                        (*pgrescued)++;
 225                unlock_page(page);
 226                return true;
 227        }
 228
 229        return false;
 230}
 231
 232/*
 233 * Putback multiple evictable pages to the LRU
 234 *
 235 * Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
 236 * the pages might have meanwhile become unevictable but that is OK.
 237 */
 238static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
 239{
 240        count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
 241        /*
 242         *__pagevec_lru_add() calls release_pages() so we don't call
 243         * put_page() explicitly
 244         */
 245        __pagevec_lru_add(pvec);
 246        count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
 247}
 248
 249/*
 250 * Munlock a batch of pages from the same zone
 251 *
 252 * The work is split to two main phases. First phase clears the Mlocked flag
 253 * and attempts to isolate the pages, all under a single zone lru lock.
 254 * The second phase finishes the munlock only for pages where isolation
 255 * succeeded.
 256 *
 257 * Note that the pagevec may be modified during the process.
 258 */
 259static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
 260{
 261        int i;
 262        int nr = pagevec_count(pvec);
 263        int delta_munlocked = -nr;
 264        struct pagevec pvec_putback;
 265        struct lruvec *lruvec = NULL;
 266        int pgrescued = 0;
 267
 268        pagevec_init(&pvec_putback);
 269
 270        /* Phase 1: page isolation */
 271        for (i = 0; i < nr; i++) {
 272                struct page *page = pvec->pages[i];
 273
 274                if (TestClearPageMlocked(page)) {
 275                        /*
 276                         * We already have pin from follow_page_mask()
 277                         * so we can spare the get_page() here.
 278                         */
 279                        if (TestClearPageLRU(page)) {
 280                                lruvec = relock_page_lruvec_irq(page, lruvec);
 281                                del_page_from_lru_list(page, lruvec);
 282                                continue;
 283                        } else
 284                                __munlock_isolation_failed(page);
 285                } else {
 286                        delta_munlocked++;
 287                }
 288
 289                /*
 290                 * We won't be munlocking this page in the next phase
 291                 * but we still need to release the follow_page_mask()
 292                 * pin. We cannot do it under lru_lock however. If it's
 293                 * the last pin, __page_cache_release() would deadlock.
 294                 */
 295                pagevec_add(&pvec_putback, pvec->pages[i]);
 296                pvec->pages[i] = NULL;
 297        }
 298        if (lruvec) {
 299                __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
 300                unlock_page_lruvec_irq(lruvec);
 301        } else if (delta_munlocked) {
 302                mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
 303        }
 304
 305        /* Now we can release pins of pages that we are not munlocking */
 306        pagevec_release(&pvec_putback);
 307
 308        /* Phase 2: page munlock */
 309        for (i = 0; i < nr; i++) {
 310                struct page *page = pvec->pages[i];
 311
 312                if (page) {
 313                        lock_page(page);
 314                        if (!__putback_lru_fast_prepare(page, &pvec_putback,
 315                                        &pgrescued)) {
 316                                /*
 317                                 * Slow path. We don't want to lose the last
 318                                 * pin before unlock_page()
 319                                 */
 320                                get_page(page); /* for putback_lru_page() */
 321                                __munlock_isolated_page(page);
 322                                unlock_page(page);
 323                                put_page(page); /* from follow_page_mask() */
 324                        }
 325                }
 326        }
 327
 328        /*
 329         * Phase 3: page putback for pages that qualified for the fast path
 330         * This will also call put_page() to return pin from follow_page_mask()
 331         */
 332        if (pagevec_count(&pvec_putback))
 333                __putback_lru_fast(&pvec_putback, pgrescued);
 334}
 335
 336/*
 337 * Fill up pagevec for __munlock_pagevec using pte walk
 338 *
 339 * The function expects that the struct page corresponding to @start address is
 340 * a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
 341 *
 342 * The rest of @pvec is filled by subsequent pages within the same pmd and same
 343 * zone, as long as the pte's are present and vm_normal_page() succeeds. These
 344 * pages also get pinned.
 345 *
 346 * Returns the address of the next page that should be scanned. This equals
 347 * @start + PAGE_SIZE when no page could be added by the pte walk.
 348 */
 349static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
 350                        struct vm_area_struct *vma, struct zone *zone,
 351                        unsigned long start, unsigned long end)
 352{
 353        pte_t *pte;
 354        spinlock_t *ptl;
 355
 356        /*
 357         * Initialize pte walk starting at the already pinned page where we
 358         * are sure that there is a pte, as it was pinned under the same
 359         * mmap_lock write op.
 360         */
 361        pte = get_locked_pte(vma->vm_mm, start, &ptl);
 362        /* Make sure we do not cross the page table boundary */
 363        end = pgd_addr_end(start, end);
 364        end = p4d_addr_end(start, end);
 365        end = pud_addr_end(start, end);
 366        end = pmd_addr_end(start, end);
 367
 368        /* The page next to the pinned page is the first we will try to get */
 369        start += PAGE_SIZE;
 370        while (start < end) {
 371                struct page *page = NULL;
 372                pte++;
 373                if (pte_present(*pte))
 374                        page = vm_normal_page(vma, start, *pte);
 375                /*
 376                 * Break if page could not be obtained or the page's node+zone does not
 377                 * match
 378                 */
 379                if (!page || page_zone(page) != zone)
 380                        break;
 381
 382                /*
 383                 * Do not use pagevec for PTE-mapped THP,
 384                 * munlock_vma_pages_range() will handle them.
 385                 */
 386                if (PageTransCompound(page))
 387                        break;
 388
 389                get_page(page);
 390                /*
 391                 * Increase the address that will be returned *before* the
 392                 * eventual break due to pvec becoming full by adding the page
 393                 */
 394                start += PAGE_SIZE;
 395                if (pagevec_add(pvec, page) == 0)
 396                        break;
 397        }
 398        pte_unmap_unlock(pte, ptl);
 399        return start;
 400}
 401
 402/*
 403 * munlock_vma_pages_range() - munlock all pages in the vma range.'
 404 * @vma - vma containing range to be munlock()ed.
 405 * @start - start address in @vma of the range
 406 * @end - end of range in @vma.
 407 *
 408 *  For mremap(), munmap() and exit().
 409 *
 410 * Called with @vma VM_LOCKED.
 411 *
 412 * Returns with VM_LOCKED cleared.  Callers must be prepared to
 413 * deal with this.
 414 *
 415 * We don't save and restore VM_LOCKED here because pages are
 416 * still on lru.  In unmap path, pages might be scanned by reclaim
 417 * and re-mlocked by try_to_{munlock|unmap} before we unmap and
 418 * free them.  This will result in freeing mlocked pages.
 419 */
 420void munlock_vma_pages_range(struct vm_area_struct *vma,
 421                             unsigned long start, unsigned long end)
 422{
 423        vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
 424
 425        while (start < end) {
 426                struct page *page;
 427                unsigned int page_mask = 0;
 428                unsigned long page_increm;
 429                struct pagevec pvec;
 430                struct zone *zone;
 431
 432                pagevec_init(&pvec);
 433                /*
 434                 * Although FOLL_DUMP is intended for get_dump_page(),
 435                 * it just so happens that its special treatment of the
 436                 * ZERO_PAGE (returning an error instead of doing get_page)
 437                 * suits munlock very well (and if somehow an abnormal page
 438                 * has sneaked into the range, we won't oops here: great).
 439                 */
 440                page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
 441
 442                if (page && !IS_ERR(page)) {
 443                        if (PageTransTail(page)) {
 444                                VM_BUG_ON_PAGE(PageMlocked(page), page);
 445                                put_page(page); /* follow_page_mask() */
 446                        } else if (PageTransHuge(page)) {
 447                                lock_page(page);
 448                                /*
 449                                 * Any THP page found by follow_page_mask() may
 450                                 * have gotten split before reaching
 451                                 * munlock_vma_page(), so we need to compute
 452                                 * the page_mask here instead.
 453                                 */
 454                                page_mask = munlock_vma_page(page);
 455                                unlock_page(page);
 456                                put_page(page); /* follow_page_mask() */
 457                        } else {
 458                                /*
 459                                 * Non-huge pages are handled in batches via
 460                                 * pagevec. The pin from follow_page_mask()
 461                                 * prevents them from collapsing by THP.
 462                                 */
 463                                pagevec_add(&pvec, page);
 464                                zone = page_zone(page);
 465
 466                                /*
 467                                 * Try to fill the rest of pagevec using fast
 468                                 * pte walk. This will also update start to
 469                                 * the next page to process. Then munlock the
 470                                 * pagevec.
 471                                 */
 472                                start = __munlock_pagevec_fill(&pvec, vma,
 473                                                zone, start, end);
 474                                __munlock_pagevec(&pvec, zone);
 475                                goto next;
 476                        }
 477                }
 478                page_increm = 1 + page_mask;
 479                start += page_increm * PAGE_SIZE;
 480next:
 481                cond_resched();
 482        }
 483}
 484
 485/*
 486 * mlock_fixup  - handle mlock[all]/munlock[all] requests.
 487 *
 488 * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
 489 * munlock is a no-op.  However, for some special vmas, we go ahead and
 490 * populate the ptes.
 491 *
 492 * For vmas that pass the filters, merge/split as appropriate.
 493 */
 494static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 495        unsigned long start, unsigned long end, vm_flags_t newflags)
 496{
 497        struct mm_struct *mm = vma->vm_mm;
 498        pgoff_t pgoff;
 499        int nr_pages;
 500        int ret = 0;
 501        int lock = !!(newflags & VM_LOCKED);
 502        vm_flags_t old_flags = vma->vm_flags;
 503
 504        if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
 505            is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
 506            vma_is_dax(vma))
 507                /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
 508                goto out;
 509
 510        pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 511        *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
 512                          vma->vm_file, pgoff, vma_policy(vma),
 513                          vma->vm_userfaultfd_ctx);
 514        if (*prev) {
 515                vma = *prev;
 516                goto success;
 517        }
 518
 519        if (start != vma->vm_start) {
 520                ret = split_vma(mm, vma, start, 1);
 521                if (ret)
 522                        goto out;
 523        }
 524
 525        if (end != vma->vm_end) {
 526                ret = split_vma(mm, vma, end, 0);
 527                if (ret)
 528                        goto out;
 529        }
 530
 531success:
 532        /*
 533         * Keep track of amount of locked VM.
 534         */
 535        nr_pages = (end - start) >> PAGE_SHIFT;
 536        if (!lock)
 537                nr_pages = -nr_pages;
 538        else if (old_flags & VM_LOCKED)
 539                nr_pages = 0;
 540        mm->locked_vm += nr_pages;
 541
 542        /*
 543         * vm_flags is protected by the mmap_lock held in write mode.
 544         * It's okay if try_to_unmap_one unmaps a page just after we
 545         * set VM_LOCKED, populate_vma_page_range will bring it back.
 546         */
 547
 548        if (lock)
 549                vma->vm_flags = newflags;
 550        else
 551                munlock_vma_pages_range(vma, start, end);
 552
 553out:
 554        *prev = vma;
 555        return ret;
 556}
 557
 558static int apply_vma_lock_flags(unsigned long start, size_t len,
 559                                vm_flags_t flags)
 560{
 561        unsigned long nstart, end, tmp;
 562        struct vm_area_struct *vma, *prev;
 563        int error;
 564
 565        VM_BUG_ON(offset_in_page(start));
 566        VM_BUG_ON(len != PAGE_ALIGN(len));
 567        end = start + len;
 568        if (end < start)
 569                return -EINVAL;
 570        if (end == start)
 571                return 0;
 572        vma = find_vma(current->mm, start);
 573        if (!vma || vma->vm_start > start)
 574                return -ENOMEM;
 575
 576        prev = vma->vm_prev;
 577        if (start > vma->vm_start)
 578                prev = vma;
 579
 580        for (nstart = start ; ; ) {
 581                vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
 582
 583                newflags |= flags;
 584
 585                /* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
 586                tmp = vma->vm_end;
 587                if (tmp > end)
 588                        tmp = end;
 589                error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
 590                if (error)
 591                        break;
 592                nstart = tmp;
 593                if (nstart < prev->vm_end)
 594                        nstart = prev->vm_end;
 595                if (nstart >= end)
 596                        break;
 597
 598                vma = prev->vm_next;
 599                if (!vma || vma->vm_start != nstart) {
 600                        error = -ENOMEM;
 601                        break;
 602                }
 603        }
 604        return error;
 605}
 606
 607/*
 608 * Go through vma areas and sum size of mlocked
 609 * vma pages, as return value.
 610 * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
 611 * is also counted.
 612 * Return value: previously mlocked page counts
 613 */
 614static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
 615                unsigned long start, size_t len)
 616{
 617        struct vm_area_struct *vma;
 618        unsigned long count = 0;
 619
 620        if (mm == NULL)
 621                mm = current->mm;
 622
 623        vma = find_vma(mm, start);
 624        if (vma == NULL)
 625                return 0;
 626
 627        for (; vma ; vma = vma->vm_next) {
 628                if (start >= vma->vm_end)
 629                        continue;
 630                if (start + len <=  vma->vm_start)
 631                        break;
 632                if (vma->vm_flags & VM_LOCKED) {
 633                        if (start > vma->vm_start)
 634                                count -= (start - vma->vm_start);
 635                        if (start + len < vma->vm_end) {
 636                                count += start + len - vma->vm_start;
 637                                break;
 638                        }
 639                        count += vma->vm_end - vma->vm_start;
 640                }
 641        }
 642
 643        return count >> PAGE_SHIFT;
 644}
 645
 646static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
 647{
 648        unsigned long locked;
 649        unsigned long lock_limit;
 650        int error = -ENOMEM;
 651
 652        start = untagged_addr(start);
 653
 654        if (!can_do_mlock())
 655                return -EPERM;
 656
 657        len = PAGE_ALIGN(len + (offset_in_page(start)));
 658        start &= PAGE_MASK;
 659
 660        lock_limit = rlimit(RLIMIT_MEMLOCK);
 661        lock_limit >>= PAGE_SHIFT;
 662        locked = len >> PAGE_SHIFT;
 663
 664        if (mmap_write_lock_killable(current->mm))
 665                return -EINTR;
 666
 667        locked += current->mm->locked_vm;
 668        if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
 669                /*
 670                 * It is possible that the regions requested intersect with
 671                 * previously mlocked areas, that part area in "mm->locked_vm"
 672                 * should not be counted to new mlock increment count. So check
 673                 * and adjust locked count if necessary.
 674                 */
 675                locked -= count_mm_mlocked_page_nr(current->mm,
 676                                start, len);
 677        }
 678
 679        /* check against resource limits */
 680        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
 681                error = apply_vma_lock_flags(start, len, flags);
 682
 683        mmap_write_unlock(current->mm);
 684        if (error)
 685                return error;
 686
 687        error = __mm_populate(start, len, 0);
 688        if (error)
 689                return __mlock_posix_error_return(error);
 690        return 0;
 691}
 692
 693SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
 694{
 695        return do_mlock(start, len, VM_LOCKED);
 696}
 697
 698SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
 699{
 700        vm_flags_t vm_flags = VM_LOCKED;
 701
 702        if (flags & ~MLOCK_ONFAULT)
 703                return -EINVAL;
 704
 705        if (flags & MLOCK_ONFAULT)
 706                vm_flags |= VM_LOCKONFAULT;
 707
 708        return do_mlock(start, len, vm_flags);
 709}
 710
 711SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 712{
 713        int ret;
 714
 715        start = untagged_addr(start);
 716
 717        len = PAGE_ALIGN(len + (offset_in_page(start)));
 718        start &= PAGE_MASK;
 719
 720        if (mmap_write_lock_killable(current->mm))
 721                return -EINTR;
 722        ret = apply_vma_lock_flags(start, len, 0);
 723        mmap_write_unlock(current->mm);
 724
 725        return ret;
 726}
 727
 728/*
 729 * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
 730 * and translate into the appropriate modifications to mm->def_flags and/or the
 731 * flags for all current VMAs.
 732 *
 733 * There are a couple of subtleties with this.  If mlockall() is called multiple
 734 * times with different flags, the values do not necessarily stack.  If mlockall
 735 * is called once including the MCL_FUTURE flag and then a second time without
 736 * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
 737 */
 738static int apply_mlockall_flags(int flags)
 739{
 740        struct vm_area_struct *vma, *prev = NULL;
 741        vm_flags_t to_add = 0;
 742
 743        current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
 744        if (flags & MCL_FUTURE) {
 745                current->mm->def_flags |= VM_LOCKED;
 746
 747                if (flags & MCL_ONFAULT)
 748                        current->mm->def_flags |= VM_LOCKONFAULT;
 749
 750                if (!(flags & MCL_CURRENT))
 751                        goto out;
 752        }
 753
 754        if (flags & MCL_CURRENT) {
 755                to_add |= VM_LOCKED;
 756                if (flags & MCL_ONFAULT)
 757                        to_add |= VM_LOCKONFAULT;
 758        }
 759
 760        for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
 761                vm_flags_t newflags;
 762
 763                newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
 764                newflags |= to_add;
 765
 766                /* Ignore errors */
 767                mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
 768                cond_resched();
 769        }
 770out:
 771        return 0;
 772}
 773
 774SYSCALL_DEFINE1(mlockall, int, flags)
 775{
 776        unsigned long lock_limit;
 777        int ret;
 778
 779        if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
 780            flags == MCL_ONFAULT)
 781                return -EINVAL;
 782
 783        if (!can_do_mlock())
 784                return -EPERM;
 785
 786        lock_limit = rlimit(RLIMIT_MEMLOCK);
 787        lock_limit >>= PAGE_SHIFT;
 788
 789        if (mmap_write_lock_killable(current->mm))
 790                return -EINTR;
 791
 792        ret = -ENOMEM;
 793        if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
 794            capable(CAP_IPC_LOCK))
 795                ret = apply_mlockall_flags(flags);
 796        mmap_write_unlock(current->mm);
 797        if (!ret && (flags & MCL_CURRENT))
 798                mm_populate(0, TASK_SIZE);
 799
 800        return ret;
 801}
 802
 803SYSCALL_DEFINE0(munlockall)
 804{
 805        int ret;
 806
 807        if (mmap_write_lock_killable(current->mm))
 808                return -EINTR;
 809        ret = apply_mlockall_flags(0);
 810        mmap_write_unlock(current->mm);
 811        return ret;
 812}
 813
 814/*
 815 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
 816 * shm segments) get accounted against the user_struct instead.
 817 */
 818static DEFINE_SPINLOCK(shmlock_user_lock);
 819
 820int user_shm_lock(size_t size, struct user_struct *user)
 821{
 822        unsigned long lock_limit, locked;
 823        int allowed = 0;
 824
 825        locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 826        lock_limit = rlimit(RLIMIT_MEMLOCK);
 827        if (lock_limit == RLIM_INFINITY)
 828                allowed = 1;
 829        lock_limit >>= PAGE_SHIFT;
 830        spin_lock(&shmlock_user_lock);
 831        if (!allowed &&
 832            locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
 833                goto out;
 834        get_uid(user);
 835        user->locked_shm += locked;
 836        allowed = 1;
 837out:
 838        spin_unlock(&shmlock_user_lock);
 839        return allowed;
 840}
 841
 842void user_shm_unlock(size_t size, struct user_struct *user)
 843{
 844        spin_lock(&shmlock_user_lock);
 845        user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 846        spin_unlock(&shmlock_user_lock);
 847        free_uid(user);
 848}
 849