linux/mm/memory.c
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   1/*
   2 *  linux/mm/memory.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5 */
   6
   7/*
   8 * demand-loading started 01.12.91 - seems it is high on the list of
   9 * things wanted, and it should be easy to implement. - Linus
  10 */
  11
  12/*
  13 * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
  14 * pages started 02.12.91, seems to work. - Linus.
  15 *
  16 * Tested sharing by executing about 30 /bin/sh: under the old kernel it
  17 * would have taken more than the 6M I have free, but it worked well as
  18 * far as I could see.
  19 *
  20 * Also corrected some "invalidate()"s - I wasn't doing enough of them.
  21 */
  22
  23/*
  24 * Real VM (paging to/from disk) started 18.12.91. Much more work and
  25 * thought has to go into this. Oh, well..
  26 * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
  27 *              Found it. Everything seems to work now.
  28 * 20.12.91  -  Ok, making the swap-device changeable like the root.
  29 */
  30
  31/*
  32 * 05.04.94  -  Multi-page memory management added for v1.1.
  33 *              Idea by Alex Bligh (alex@cconcepts.co.uk)
  34 *
  35 * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
  36 *              (Gerhard.Wichert@pdb.siemens.de)
  37 *
  38 * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
  39 */
  40
  41#include <linux/kernel_stat.h>
  42#include <linux/mm.h>
  43#include <linux/hugetlb.h>
  44#include <linux/mman.h>
  45#include <linux/swap.h>
  46#include <linux/highmem.h>
  47#include <linux/pagemap.h>
  48#include <linux/rmap.h>
  49#include <linux/module.h>
  50#include <linux/delayacct.h>
  51#include <linux/init.h>
  52#include <linux/writeback.h>
  53#include <linux/memcontrol.h>
  54#include <linux/mmu_notifier.h>
  55
  56#include <asm/pgalloc.h>
  57#include <asm/uaccess.h>
  58#include <asm/tlb.h>
  59#include <asm/tlbflush.h>
  60#include <asm/pgtable.h>
  61
  62#include <linux/swapops.h>
  63#include <linux/elf.h>
  64
  65#include "internal.h"
  66
  67#ifndef CONFIG_NEED_MULTIPLE_NODES
  68/* use the per-pgdat data instead for discontigmem - mbligh */
  69unsigned long max_mapnr;
  70struct page *mem_map;
  71
  72EXPORT_SYMBOL(max_mapnr);
  73EXPORT_SYMBOL(mem_map);
  74#endif
  75
  76unsigned long num_physpages;
  77/*
  78 * A number of key systems in x86 including ioremap() rely on the assumption
  79 * that high_memory defines the upper bound on direct map memory, then end
  80 * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
  81 * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
  82 * and ZONE_HIGHMEM.
  83 */
  84void * high_memory;
  85
  86EXPORT_SYMBOL(num_physpages);
  87EXPORT_SYMBOL(high_memory);
  88
  89/*
  90 * Randomize the address space (stacks, mmaps, brk, etc.).
  91 *
  92 * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
  93 *   as ancient (libc5 based) binaries can segfault. )
  94 */
  95int randomize_va_space __read_mostly =
  96#ifdef CONFIG_COMPAT_BRK
  97                                        1;
  98#else
  99                                        2;
 100#endif
 101
 102static int __init disable_randmaps(char *s)
 103{
 104        randomize_va_space = 0;
 105        return 1;
 106}
 107__setup("norandmaps", disable_randmaps);
 108
 109
 110/*
 111 * If a p?d_bad entry is found while walking page tables, report
 112 * the error, before resetting entry to p?d_none.  Usually (but
 113 * very seldom) called out from the p?d_none_or_clear_bad macros.
 114 */
 115
 116void pgd_clear_bad(pgd_t *pgd)
 117{
 118        pgd_ERROR(*pgd);
 119        pgd_clear(pgd);
 120}
 121
 122void pud_clear_bad(pud_t *pud)
 123{
 124        pud_ERROR(*pud);
 125        pud_clear(pud);
 126}
 127
 128void pmd_clear_bad(pmd_t *pmd)
 129{
 130        pmd_ERROR(*pmd);
 131        pmd_clear(pmd);
 132}
 133
 134/*
 135 * Note: this doesn't free the actual pages themselves. That
 136 * has been handled earlier when unmapping all the memory regions.
 137 */
 138static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd)
 139{
 140        pgtable_t token = pmd_pgtable(*pmd);
 141        pmd_clear(pmd);
 142        pte_free_tlb(tlb, token);
 143        tlb->mm->nr_ptes--;
 144}
 145
 146static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
 147                                unsigned long addr, unsigned long end,
 148                                unsigned long floor, unsigned long ceiling)
 149{
 150        pmd_t *pmd;
 151        unsigned long next;
 152        unsigned long start;
 153
 154        start = addr;
 155        pmd = pmd_offset(pud, addr);
 156        do {
 157                next = pmd_addr_end(addr, end);
 158                if (pmd_none_or_clear_bad(pmd))
 159                        continue;
 160                free_pte_range(tlb, pmd);
 161        } while (pmd++, addr = next, addr != end);
 162
 163        start &= PUD_MASK;
 164        if (start < floor)
 165                return;
 166        if (ceiling) {
 167                ceiling &= PUD_MASK;
 168                if (!ceiling)
 169                        return;
 170        }
 171        if (end - 1 > ceiling - 1)
 172                return;
 173
 174        pmd = pmd_offset(pud, start);
 175        pud_clear(pud);
 176        pmd_free_tlb(tlb, pmd);
 177}
 178
 179static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
 180                                unsigned long addr, unsigned long end,
 181                                unsigned long floor, unsigned long ceiling)
 182{
 183        pud_t *pud;
 184        unsigned long next;
 185        unsigned long start;
 186
 187        start = addr;
 188        pud = pud_offset(pgd, addr);
 189        do {
 190                next = pud_addr_end(addr, end);
 191                if (pud_none_or_clear_bad(pud))
 192                        continue;
 193                free_pmd_range(tlb, pud, addr, next, floor, ceiling);
 194        } while (pud++, addr = next, addr != end);
 195
 196        start &= PGDIR_MASK;
 197        if (start < floor)
 198                return;
 199        if (ceiling) {
 200                ceiling &= PGDIR_MASK;
 201                if (!ceiling)
 202                        return;
 203        }
 204        if (end - 1 > ceiling - 1)
 205                return;
 206
 207        pud = pud_offset(pgd, start);
 208        pgd_clear(pgd);
 209        pud_free_tlb(tlb, pud);
 210}
 211
 212/*
 213 * This function frees user-level page tables of a process.
 214 *
 215 * Must be called with pagetable lock held.
 216 */
 217void free_pgd_range(struct mmu_gather *tlb,
 218                        unsigned long addr, unsigned long end,
 219                        unsigned long floor, unsigned long ceiling)
 220{
 221        pgd_t *pgd;
 222        unsigned long next;
 223        unsigned long start;
 224
 225        /*
 226         * The next few lines have given us lots of grief...
 227         *
 228         * Why are we testing PMD* at this top level?  Because often
 229         * there will be no work to do at all, and we'd prefer not to
 230         * go all the way down to the bottom just to discover that.
 231         *
 232         * Why all these "- 1"s?  Because 0 represents both the bottom
 233         * of the address space and the top of it (using -1 for the
 234         * top wouldn't help much: the masks would do the wrong thing).
 235         * The rule is that addr 0 and floor 0 refer to the bottom of
 236         * the address space, but end 0 and ceiling 0 refer to the top
 237         * Comparisons need to use "end - 1" and "ceiling - 1" (though
 238         * that end 0 case should be mythical).
 239         *
 240         * Wherever addr is brought up or ceiling brought down, we must
 241         * be careful to reject "the opposite 0" before it confuses the
 242         * subsequent tests.  But what about where end is brought down
 243         * by PMD_SIZE below? no, end can't go down to 0 there.
 244         *
 245         * Whereas we round start (addr) and ceiling down, by different
 246         * masks at different levels, in order to test whether a table
 247         * now has no other vmas using it, so can be freed, we don't
 248         * bother to round floor or end up - the tests don't need that.
 249         */
 250
 251        addr &= PMD_MASK;
 252        if (addr < floor) {
 253                addr += PMD_SIZE;
 254                if (!addr)
 255                        return;
 256        }
 257        if (ceiling) {
 258                ceiling &= PMD_MASK;
 259                if (!ceiling)
 260                        return;
 261        }
 262        if (end - 1 > ceiling - 1)
 263                end -= PMD_SIZE;
 264        if (addr > end - 1)
 265                return;
 266
 267        start = addr;
 268        pgd = pgd_offset(tlb->mm, addr);
 269        do {
 270                next = pgd_addr_end(addr, end);
 271                if (pgd_none_or_clear_bad(pgd))
 272                        continue;
 273                free_pud_range(tlb, pgd, addr, next, floor, ceiling);
 274        } while (pgd++, addr = next, addr != end);
 275}
 276
 277void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
 278                unsigned long floor, unsigned long ceiling)
 279{
 280        while (vma) {
 281                struct vm_area_struct *next = vma->vm_next;
 282                unsigned long addr = vma->vm_start;
 283
 284                /*
 285                 * Hide vma from rmap and vmtruncate before freeing pgtables
 286                 */
 287                anon_vma_unlink(vma);
 288                unlink_file_vma(vma);
 289
 290                if (is_vm_hugetlb_page(vma)) {
 291                        hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
 292                                floor, next? next->vm_start: ceiling);
 293                } else {
 294                        /*
 295                         * Optimization: gather nearby vmas into one call down
 296                         */
 297                        while (next && next->vm_start <= vma->vm_end + PMD_SIZE
 298                               && !is_vm_hugetlb_page(next)) {
 299                                vma = next;
 300                                next = vma->vm_next;
 301                                anon_vma_unlink(vma);
 302                                unlink_file_vma(vma);
 303                        }
 304                        free_pgd_range(tlb, addr, vma->vm_end,
 305                                floor, next? next->vm_start: ceiling);
 306                }
 307                vma = next;
 308        }
 309}
 310
 311int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
 312{
 313        pgtable_t new = pte_alloc_one(mm, address);
 314        if (!new)
 315                return -ENOMEM;
 316
 317        /*
 318         * Ensure all pte setup (eg. pte page lock and page clearing) are
 319         * visible before the pte is made visible to other CPUs by being
 320         * put into page tables.
 321         *
 322         * The other side of the story is the pointer chasing in the page
 323         * table walking code (when walking the page table without locking;
 324         * ie. most of the time). Fortunately, these data accesses consist
 325         * of a chain of data-dependent loads, meaning most CPUs (alpha
 326         * being the notable exception) will already guarantee loads are
 327         * seen in-order. See the alpha page table accessors for the
 328         * smp_read_barrier_depends() barriers in page table walking code.
 329         */
 330        smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
 331
 332        spin_lock(&mm->page_table_lock);
 333        if (!pmd_present(*pmd)) {       /* Has another populated it ? */
 334                mm->nr_ptes++;
 335                pmd_populate(mm, pmd, new);
 336                new = NULL;
 337        }
 338        spin_unlock(&mm->page_table_lock);
 339        if (new)
 340                pte_free(mm, new);
 341        return 0;
 342}
 343
 344int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
 345{
 346        pte_t *new = pte_alloc_one_kernel(&init_mm, address);
 347        if (!new)
 348                return -ENOMEM;
 349
 350        smp_wmb(); /* See comment in __pte_alloc */
 351
 352        spin_lock(&init_mm.page_table_lock);
 353        if (!pmd_present(*pmd)) {       /* Has another populated it ? */
 354                pmd_populate_kernel(&init_mm, pmd, new);
 355                new = NULL;
 356        }
 357        spin_unlock(&init_mm.page_table_lock);
 358        if (new)
 359                pte_free_kernel(&init_mm, new);
 360        return 0;
 361}
 362
 363static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
 364{
 365        if (file_rss)
 366                add_mm_counter(mm, file_rss, file_rss);
 367        if (anon_rss)
 368                add_mm_counter(mm, anon_rss, anon_rss);
 369}
 370
 371/*
 372 * This function is called to print an error when a bad pte
 373 * is found. For example, we might have a PFN-mapped pte in
 374 * a region that doesn't allow it.
 375 *
 376 * The calling function must still handle the error.
 377 */
 378static void print_bad_pte(struct vm_area_struct *vma, pte_t pte,
 379                          unsigned long vaddr)
 380{
 381        printk(KERN_ERR "Bad pte = %08llx, process = %s, "
 382                        "vm_flags = %lx, vaddr = %lx\n",
 383                (long long)pte_val(pte),
 384                (vma->vm_mm == current->mm ? current->comm : "???"),
 385                vma->vm_flags, vaddr);
 386        dump_stack();
 387}
 388
 389static inline int is_cow_mapping(unsigned int flags)
 390{
 391        return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 392}
 393
 394/*
 395 * vm_normal_page -- This function gets the "struct page" associated with a pte.
 396 *
 397 * "Special" mappings do not wish to be associated with a "struct page" (either
 398 * it doesn't exist, or it exists but they don't want to touch it). In this
 399 * case, NULL is returned here. "Normal" mappings do have a struct page.
 400 *
 401 * There are 2 broad cases. Firstly, an architecture may define a pte_special()
 402 * pte bit, in which case this function is trivial. Secondly, an architecture
 403 * may not have a spare pte bit, which requires a more complicated scheme,
 404 * described below.
 405 *
 406 * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
 407 * special mapping (even if there are underlying and valid "struct pages").
 408 * COWed pages of a VM_PFNMAP are always normal.
 409 *
 410 * The way we recognize COWed pages within VM_PFNMAP mappings is through the
 411 * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
 412 * set, and the vm_pgoff will point to the first PFN mapped: thus every special
 413 * mapping will always honor the rule
 414 *
 415 *      pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
 416 *
 417 * And for normal mappings this is false.
 418 *
 419 * This restricts such mappings to be a linear translation from virtual address
 420 * to pfn. To get around this restriction, we allow arbitrary mappings so long
 421 * as the vma is not a COW mapping; in that case, we know that all ptes are
 422 * special (because none can have been COWed).
 423 *
 424 *
 425 * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
 426 *
 427 * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
 428 * page" backing, however the difference is that _all_ pages with a struct
 429 * page (that is, those where pfn_valid is true) are refcounted and considered
 430 * normal pages by the VM. The disadvantage is that pages are refcounted
 431 * (which can be slower and simply not an option for some PFNMAP users). The
 432 * advantage is that we don't have to follow the strict linearity rule of
 433 * PFNMAP mappings in order to support COWable mappings.
 434 *
 435 */
 436#ifdef __HAVE_ARCH_PTE_SPECIAL
 437# define HAVE_PTE_SPECIAL 1
 438#else
 439# define HAVE_PTE_SPECIAL 0
 440#endif
 441struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 442                                pte_t pte)
 443{
 444        unsigned long pfn;
 445
 446        if (HAVE_PTE_SPECIAL) {
 447                if (likely(!pte_special(pte))) {
 448                        VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 449                        return pte_page(pte);
 450                }
 451                VM_BUG_ON(!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)));
 452                return NULL;
 453        }
 454
 455        /* !HAVE_PTE_SPECIAL case follows: */
 456
 457        pfn = pte_pfn(pte);
 458
 459        if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
 460                if (vma->vm_flags & VM_MIXEDMAP) {
 461                        if (!pfn_valid(pfn))
 462                                return NULL;
 463                        goto out;
 464                } else {
 465                        unsigned long off;
 466                        off = (addr - vma->vm_start) >> PAGE_SHIFT;
 467                        if (pfn == vma->vm_pgoff + off)
 468                                return NULL;
 469                        if (!is_cow_mapping(vma->vm_flags))
 470                                return NULL;
 471                }
 472        }
 473
 474        VM_BUG_ON(!pfn_valid(pfn));
 475
 476        /*
 477         * NOTE! We still have PageReserved() pages in the page tables.
 478         *
 479         * eg. VDSO mappings can cause them to exist.
 480         */
 481out:
 482        return pfn_to_page(pfn);
 483}
 484
 485/*
 486 * copy one vm_area from one task to the other. Assumes the page tables
 487 * already present in the new task to be cleared in the whole range
 488 * covered by this vma.
 489 */
 490
 491static inline void
 492copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 493                pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
 494                unsigned long addr, int *rss)
 495{
 496        unsigned long vm_flags = vma->vm_flags;
 497        pte_t pte = *src_pte;
 498        struct page *page;
 499
 500        /* pte contains position in swap or file, so copy. */
 501        if (unlikely(!pte_present(pte))) {
 502                if (!pte_file(pte)) {
 503                        swp_entry_t entry = pte_to_swp_entry(pte);
 504
 505                        swap_duplicate(entry);
 506                        /* make sure dst_mm is on swapoff's mmlist. */
 507                        if (unlikely(list_empty(&dst_mm->mmlist))) {
 508                                spin_lock(&mmlist_lock);
 509                                if (list_empty(&dst_mm->mmlist))
 510                                        list_add(&dst_mm->mmlist,
 511                                                 &src_mm->mmlist);
 512                                spin_unlock(&mmlist_lock);
 513                        }
 514                        if (is_write_migration_entry(entry) &&
 515                                        is_cow_mapping(vm_flags)) {
 516                                /*
 517                                 * COW mappings require pages in both parent
 518                                 * and child to be set to read.
 519                                 */
 520                                make_migration_entry_read(&entry);
 521                                pte = swp_entry_to_pte(entry);
 522                                set_pte_at(src_mm, addr, src_pte, pte);
 523                        }
 524                }
 525                goto out_set_pte;
 526        }
 527
 528        /*
 529         * If it's a COW mapping, write protect it both
 530         * in the parent and the child
 531         */
 532        if (is_cow_mapping(vm_flags)) {
 533                ptep_set_wrprotect(src_mm, addr, src_pte);
 534                pte = pte_wrprotect(pte);
 535        }
 536
 537        /*
 538         * If it's a shared mapping, mark it clean in
 539         * the child
 540         */
 541        if (vm_flags & VM_SHARED)
 542                pte = pte_mkclean(pte);
 543        pte = pte_mkold(pte);
 544
 545        page = vm_normal_page(vma, addr, pte);
 546        if (page) {
 547                get_page(page);
 548                page_dup_rmap(page, vma, addr);
 549                rss[!!PageAnon(page)]++;
 550        }
 551
 552out_set_pte:
 553        set_pte_at(dst_mm, addr, dst_pte, pte);
 554}
 555
 556static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 557                pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
 558                unsigned long addr, unsigned long end)
 559{
 560        pte_t *src_pte, *dst_pte;
 561        spinlock_t *src_ptl, *dst_ptl;
 562        int progress = 0;
 563        int rss[2];
 564
 565again:
 566        rss[1] = rss[0] = 0;
 567        dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
 568        if (!dst_pte)
 569                return -ENOMEM;
 570        src_pte = pte_offset_map_nested(src_pmd, addr);
 571        src_ptl = pte_lockptr(src_mm, src_pmd);
 572        spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 573        arch_enter_lazy_mmu_mode();
 574
 575        do {
 576                /*
 577                 * We are holding two locks at this point - either of them
 578                 * could generate latencies in another task on another CPU.
 579                 */
 580                if (progress >= 32) {
 581                        progress = 0;
 582                        if (need_resched() ||
 583                            spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
 584                                break;
 585                }
 586                if (pte_none(*src_pte)) {
 587                        progress++;
 588                        continue;
 589                }
 590                copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vma, addr, rss);
 591                progress += 8;
 592        } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
 593
 594        arch_leave_lazy_mmu_mode();
 595        spin_unlock(src_ptl);
 596        pte_unmap_nested(src_pte - 1);
 597        add_mm_rss(dst_mm, rss[0], rss[1]);
 598        pte_unmap_unlock(dst_pte - 1, dst_ptl);
 599        cond_resched();
 600        if (addr != end)
 601                goto again;
 602        return 0;
 603}
 604
 605static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 606                pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
 607                unsigned long addr, unsigned long end)
 608{
 609        pmd_t *src_pmd, *dst_pmd;
 610        unsigned long next;
 611
 612        dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
 613        if (!dst_pmd)
 614                return -ENOMEM;
 615        src_pmd = pmd_offset(src_pud, addr);
 616        do {
 617                next = pmd_addr_end(addr, end);
 618                if (pmd_none_or_clear_bad(src_pmd))
 619                        continue;
 620                if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
 621                                                vma, addr, next))
 622                        return -ENOMEM;
 623        } while (dst_pmd++, src_pmd++, addr = next, addr != end);
 624        return 0;
 625}
 626
 627static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 628                pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
 629                unsigned long addr, unsigned long end)
 630{
 631        pud_t *src_pud, *dst_pud;
 632        unsigned long next;
 633
 634        dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
 635        if (!dst_pud)
 636                return -ENOMEM;
 637        src_pud = pud_offset(src_pgd, addr);
 638        do {
 639                next = pud_addr_end(addr, end);
 640                if (pud_none_or_clear_bad(src_pud))
 641                        continue;
 642                if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
 643                                                vma, addr, next))
 644                        return -ENOMEM;
 645        } while (dst_pud++, src_pud++, addr = next, addr != end);
 646        return 0;
 647}
 648
 649int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 650                struct vm_area_struct *vma)
 651{
 652        pgd_t *src_pgd, *dst_pgd;
 653        unsigned long next;
 654        unsigned long addr = vma->vm_start;
 655        unsigned long end = vma->vm_end;
 656        int ret;
 657
 658        /*
 659         * Don't copy ptes where a page fault will fill them correctly.
 660         * Fork becomes much lighter when there are big shared or private
 661         * readonly mappings. The tradeoff is that copy_page_range is more
 662         * efficient than faulting.
 663         */
 664        if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
 665                if (!vma->anon_vma)
 666                        return 0;
 667        }
 668
 669        if (is_vm_hugetlb_page(vma))
 670                return copy_hugetlb_page_range(dst_mm, src_mm, vma);
 671
 672        /*
 673         * We need to invalidate the secondary MMU mappings only when
 674         * there could be a permission downgrade on the ptes of the
 675         * parent mm. And a permission downgrade will only happen if
 676         * is_cow_mapping() returns true.
 677         */
 678        if (is_cow_mapping(vma->vm_flags))
 679                mmu_notifier_invalidate_range_start(src_mm, addr, end);
 680
 681        ret = 0;
 682        dst_pgd = pgd_offset(dst_mm, addr);
 683        src_pgd = pgd_offset(src_mm, addr);
 684        do {
 685                next = pgd_addr_end(addr, end);
 686                if (pgd_none_or_clear_bad(src_pgd))
 687                        continue;
 688                if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
 689                                            vma, addr, next))) {
 690                        ret = -ENOMEM;
 691                        break;
 692                }
 693        } while (dst_pgd++, src_pgd++, addr = next, addr != end);
 694
 695        if (is_cow_mapping(vma->vm_flags))
 696                mmu_notifier_invalidate_range_end(src_mm,
 697                                                  vma->vm_start, end);
 698        return ret;
 699}
 700
 701static unsigned long zap_pte_range(struct mmu_gather *tlb,
 702                                struct vm_area_struct *vma, pmd_t *pmd,
 703                                unsigned long addr, unsigned long end,
 704                                long *zap_work, struct zap_details *details)
 705{
 706        struct mm_struct *mm = tlb->mm;
 707        pte_t *pte;
 708        spinlock_t *ptl;
 709        int file_rss = 0;
 710        int anon_rss = 0;
 711
 712        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 713        arch_enter_lazy_mmu_mode();
 714        do {
 715                pte_t ptent = *pte;
 716                if (pte_none(ptent)) {
 717                        (*zap_work)--;
 718                        continue;
 719                }
 720
 721                (*zap_work) -= PAGE_SIZE;
 722
 723                if (pte_present(ptent)) {
 724                        struct page *page;
 725
 726                        page = vm_normal_page(vma, addr, ptent);
 727                        if (unlikely(details) && page) {
 728                                /*
 729                                 * unmap_shared_mapping_pages() wants to
 730                                 * invalidate cache without truncating:
 731                                 * unmap shared but keep private pages.
 732                                 */
 733                                if (details->check_mapping &&
 734                                    details->check_mapping != page->mapping)
 735                                        continue;
 736                                /*
 737                                 * Each page->index must be checked when
 738                                 * invalidating or truncating nonlinear.
 739                                 */
 740                                if (details->nonlinear_vma &&
 741                                    (page->index < details->first_index ||
 742                                     page->index > details->last_index))
 743                                        continue;
 744                        }
 745                        ptent = ptep_get_and_clear_full(mm, addr, pte,
 746                                                        tlb->fullmm);
 747                        tlb_remove_tlb_entry(tlb, pte, addr);
 748                        if (unlikely(!page))
 749                                continue;
 750                        if (unlikely(details) && details->nonlinear_vma
 751                            && linear_page_index(details->nonlinear_vma,
 752                                                addr) != page->index)
 753                                set_pte_at(mm, addr, pte,
 754                                           pgoff_to_pte(page->index));
 755                        if (PageAnon(page))
 756                                anon_rss--;
 757                        else {
 758                                if (pte_dirty(ptent))
 759                                        set_page_dirty(page);
 760                                if (pte_young(ptent))
 761                                        SetPageReferenced(page);
 762                                file_rss--;
 763                        }
 764                        page_remove_rmap(page, vma);
 765                        tlb_remove_page(tlb, page);
 766                        continue;
 767                }
 768                /*
 769                 * If details->check_mapping, we leave swap entries;
 770                 * if details->nonlinear_vma, we leave file entries.
 771                 */
 772                if (unlikely(details))
 773                        continue;
 774                if (!pte_file(ptent))
 775                        free_swap_and_cache(pte_to_swp_entry(ptent));
 776                pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 777        } while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
 778
 779        add_mm_rss(mm, file_rss, anon_rss);
 780        arch_leave_lazy_mmu_mode();
 781        pte_unmap_unlock(pte - 1, ptl);
 782
 783        return addr;
 784}
 785
 786static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
 787                                struct vm_area_struct *vma, pud_t *pud,
 788                                unsigned long addr, unsigned long end,
 789                                long *zap_work, struct zap_details *details)
 790{
 791        pmd_t *pmd;
 792        unsigned long next;
 793
 794        pmd = pmd_offset(pud, addr);
 795        do {
 796                next = pmd_addr_end(addr, end);
 797                if (pmd_none_or_clear_bad(pmd)) {
 798                        (*zap_work)--;
 799                        continue;
 800                }
 801                next = zap_pte_range(tlb, vma, pmd, addr, next,
 802                                                zap_work, details);
 803        } while (pmd++, addr = next, (addr != end && *zap_work > 0));
 804
 805        return addr;
 806}
 807
 808static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
 809                                struct vm_area_struct *vma, pgd_t *pgd,
 810                                unsigned long addr, unsigned long end,
 811                                long *zap_work, struct zap_details *details)
 812{
 813        pud_t *pud;
 814        unsigned long next;
 815
 816        pud = pud_offset(pgd, addr);
 817        do {
 818                next = pud_addr_end(addr, end);
 819                if (pud_none_or_clear_bad(pud)) {
 820                        (*zap_work)--;
 821                        continue;
 822                }
 823                next = zap_pmd_range(tlb, vma, pud, addr, next,
 824                                                zap_work, details);
 825        } while (pud++, addr = next, (addr != end && *zap_work > 0));
 826
 827        return addr;
 828}
 829
 830static unsigned long unmap_page_range(struct mmu_gather *tlb,
 831                                struct vm_area_struct *vma,
 832                                unsigned long addr, unsigned long end,
 833                                long *zap_work, struct zap_details *details)
 834{
 835        pgd_t *pgd;
 836        unsigned long next;
 837
 838        if (details && !details->check_mapping && !details->nonlinear_vma)
 839                details = NULL;
 840
 841        BUG_ON(addr >= end);
 842        tlb_start_vma(tlb, vma);
 843        pgd = pgd_offset(vma->vm_mm, addr);
 844        do {
 845                next = pgd_addr_end(addr, end);
 846                if (pgd_none_or_clear_bad(pgd)) {
 847                        (*zap_work)--;
 848                        continue;
 849                }
 850                next = zap_pud_range(tlb, vma, pgd, addr, next,
 851                                                zap_work, details);
 852        } while (pgd++, addr = next, (addr != end && *zap_work > 0));
 853        tlb_end_vma(tlb, vma);
 854
 855        return addr;
 856}
 857
 858#ifdef CONFIG_PREEMPT
 859# define ZAP_BLOCK_SIZE (8 * PAGE_SIZE)
 860#else
 861/* No preempt: go for improved straight-line efficiency */
 862# define ZAP_BLOCK_SIZE (1024 * PAGE_SIZE)
 863#endif
 864
 865/**
 866 * unmap_vmas - unmap a range of memory covered by a list of vma's
 867 * @tlbp: address of the caller's struct mmu_gather
 868 * @vma: the starting vma
 869 * @start_addr: virtual address at which to start unmapping
 870 * @end_addr: virtual address at which to end unmapping
 871 * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
 872 * @details: details of nonlinear truncation or shared cache invalidation
 873 *
 874 * Returns the end address of the unmapping (restart addr if interrupted).
 875 *
 876 * Unmap all pages in the vma list.
 877 *
 878 * We aim to not hold locks for too long (for scheduling latency reasons).
 879 * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
 880 * return the ending mmu_gather to the caller.
 881 *
 882 * Only addresses between `start' and `end' will be unmapped.
 883 *
 884 * The VMA list must be sorted in ascending virtual address order.
 885 *
 886 * unmap_vmas() assumes that the caller will flush the whole unmapped address
 887 * range after unmap_vmas() returns.  So the only responsibility here is to
 888 * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
 889 * drops the lock and schedules.
 890 */
 891unsigned long unmap_vmas(struct mmu_gather **tlbp,
 892                struct vm_area_struct *vma, unsigned long start_addr,
 893                unsigned long end_addr, unsigned long *nr_accounted,
 894                struct zap_details *details)
 895{
 896        long zap_work = ZAP_BLOCK_SIZE;
 897        unsigned long tlb_start = 0;    /* For tlb_finish_mmu */
 898        int tlb_start_valid = 0;
 899        unsigned long start = start_addr;
 900        spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
 901        int fullmm = (*tlbp)->fullmm;
 902        struct mm_struct *mm = vma->vm_mm;
 903
 904        mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
 905        for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
 906                unsigned long end;
 907
 908                start = max(vma->vm_start, start_addr);
 909                if (start >= vma->vm_end)
 910                        continue;
 911                end = min(vma->vm_end, end_addr);
 912                if (end <= vma->vm_start)
 913                        continue;
 914
 915                if (vma->vm_flags & VM_ACCOUNT)
 916                        *nr_accounted += (end - start) >> PAGE_SHIFT;
 917
 918                while (start != end) {
 919                        if (!tlb_start_valid) {
 920                                tlb_start = start;
 921                                tlb_start_valid = 1;
 922                        }
 923
 924                        if (unlikely(is_vm_hugetlb_page(vma))) {
 925                                /*
 926                                 * It is undesirable to test vma->vm_file as it
 927                                 * should be non-null for valid hugetlb area.
 928                                 * However, vm_file will be NULL in the error
 929                                 * cleanup path of do_mmap_pgoff. When
 930                                 * hugetlbfs ->mmap method fails,
 931                                 * do_mmap_pgoff() nullifies vma->vm_file
 932                                 * before calling this function to clean up.
 933                                 * Since no pte has actually been setup, it is
 934                                 * safe to do nothing in this case.
 935                                 */
 936                                if (vma->vm_file) {
 937                                        unmap_hugepage_range(vma, start, end, NULL);
 938                                        zap_work -= (end - start) /
 939                                        pages_per_huge_page(hstate_vma(vma));
 940                                }
 941
 942                                start = end;
 943                        } else
 944                                start = unmap_page_range(*tlbp, vma,
 945                                                start, end, &zap_work, details);
 946
 947                        if (zap_work > 0) {
 948                                BUG_ON(start != end);
 949                                break;
 950                        }
 951
 952                        tlb_finish_mmu(*tlbp, tlb_start, start);
 953
 954                        if (need_resched() ||
 955                                (i_mmap_lock && spin_needbreak(i_mmap_lock))) {
 956                                if (i_mmap_lock) {
 957                                        *tlbp = NULL;
 958                                        goto out;
 959                                }
 960                                cond_resched();
 961                        }
 962
 963                        *tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
 964                        tlb_start_valid = 0;
 965                        zap_work = ZAP_BLOCK_SIZE;
 966                }
 967        }
 968out:
 969        mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
 970        return start;   /* which is now the end (or restart) address */
 971}
 972
 973/**
 974 * zap_page_range - remove user pages in a given range
 975 * @vma: vm_area_struct holding the applicable pages
 976 * @address: starting address of pages to zap
 977 * @size: number of bytes to zap
 978 * @details: details of nonlinear truncation or shared cache invalidation
 979 */
 980unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
 981                unsigned long size, struct zap_details *details)
 982{
 983        struct mm_struct *mm = vma->vm_mm;
 984        struct mmu_gather *tlb;
 985        unsigned long end = address + size;
 986        unsigned long nr_accounted = 0;
 987
 988        lru_add_drain();
 989        tlb = tlb_gather_mmu(mm, 0);
 990        update_hiwater_rss(mm);
 991        end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
 992        if (tlb)
 993                tlb_finish_mmu(tlb, address, end);
 994        return end;
 995}
 996
 997/**
 998 * zap_vma_ptes - remove ptes mapping the vma
 999 * @vma: vm_area_struct holding ptes to be zapped
1000 * @address: starting address of pages to zap
1001 * @size: number of bytes to zap
1002 *
1003 * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1004 *
1005 * The entire address range must be fully contained within the vma.
1006 *
1007 * Returns 0 if successful.
1008 */
1009int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1010                unsigned long size)
1011{
1012        if (address < vma->vm_start || address + size > vma->vm_end ||
1013                        !(vma->vm_flags & VM_PFNMAP))
1014                return -1;
1015        zap_page_range(vma, address, size, NULL);
1016        return 0;
1017}
1018EXPORT_SYMBOL_GPL(zap_vma_ptes);
1019
1020/*
1021 * Do a quick page-table lookup for a single page.
1022 */
1023struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1024                        unsigned int flags)
1025{
1026        pgd_t *pgd;
1027        pud_t *pud;
1028        pmd_t *pmd;
1029        pte_t *ptep, pte;
1030        spinlock_t *ptl;
1031        struct page *page;
1032        struct mm_struct *mm = vma->vm_mm;
1033
1034        page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1035        if (!IS_ERR(page)) {
1036                BUG_ON(flags & FOLL_GET);
1037                goto out;
1038        }
1039
1040        page = NULL;
1041        pgd = pgd_offset(mm, address);
1042        if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1043                goto no_page_table;
1044
1045        pud = pud_offset(pgd, address);
1046        if (pud_none(*pud))
1047                goto no_page_table;
1048        if (pud_huge(*pud)) {
1049                BUG_ON(flags & FOLL_GET);
1050                page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1051                goto out;
1052        }
1053        if (unlikely(pud_bad(*pud)))
1054                goto no_page_table;
1055
1056        pmd = pmd_offset(pud, address);
1057        if (pmd_none(*pmd))
1058                goto no_page_table;
1059        if (pmd_huge(*pmd)) {
1060                BUG_ON(flags & FOLL_GET);
1061                page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1062                goto out;
1063        }
1064        if (unlikely(pmd_bad(*pmd)))
1065                goto no_page_table;
1066
1067        ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1068
1069        pte = *ptep;
1070        if (!pte_present(pte))
1071                goto no_page;
1072        if ((flags & FOLL_WRITE) && !pte_write(pte))
1073                goto unlock;
1074        page = vm_normal_page(vma, address, pte);
1075        if (unlikely(!page))
1076                goto bad_page;
1077
1078        if (flags & FOLL_GET)
1079                get_page(page);
1080        if (flags & FOLL_TOUCH) {
1081                if ((flags & FOLL_WRITE) &&
1082                    !pte_dirty(pte) && !PageDirty(page))
1083                        set_page_dirty(page);
1084                mark_page_accessed(page);
1085        }
1086unlock:
1087        pte_unmap_unlock(ptep, ptl);
1088out:
1089        return page;
1090
1091bad_page:
1092        pte_unmap_unlock(ptep, ptl);
1093        return ERR_PTR(-EFAULT);
1094
1095no_page:
1096        pte_unmap_unlock(ptep, ptl);
1097        if (!pte_none(pte))
1098                return page;
1099        /* Fall through to ZERO_PAGE handling */
1100no_page_table:
1101        /*
1102         * When core dumping an enormous anonymous area that nobody
1103         * has touched so far, we don't want to allocate page tables.
1104         */
1105        if (flags & FOLL_ANON) {
1106                page = ZERO_PAGE(0);
1107                if (flags & FOLL_GET)
1108                        get_page(page);
1109                BUG_ON(flags & FOLL_WRITE);
1110        }
1111        return page;
1112}
1113
1114/* Can we do the FOLL_ANON optimization? */
1115static inline int use_zero_page(struct vm_area_struct *vma)
1116{
1117        /*
1118         * We don't want to optimize FOLL_ANON for make_pages_present()
1119         * when it tries to page in a VM_LOCKED region. As to VM_SHARED,
1120         * we want to get the page from the page tables to make sure
1121         * that we serialize and update with any other user of that
1122         * mapping.
1123         */
1124        if (vma->vm_flags & (VM_LOCKED | VM_SHARED))
1125                return 0;
1126        /*
1127         * And if we have a fault routine, it's not an anonymous region.
1128         */
1129        return !vma->vm_ops || !vma->vm_ops->fault;
1130}
1131
1132
1133
1134int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1135                     unsigned long start, int len, int flags,
1136                struct page **pages, struct vm_area_struct **vmas)
1137{
1138        int i;
1139        unsigned int vm_flags = 0;
1140        int write = !!(flags & GUP_FLAGS_WRITE);
1141        int force = !!(flags & GUP_FLAGS_FORCE);
1142        int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
1143
1144        if (len <= 0)
1145                return 0;
1146        /* 
1147         * Require read or write permissions.
1148         * If 'force' is set, we only require the "MAY" flags.
1149         */
1150        vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1151        vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1152        i = 0;
1153
1154        do {
1155                struct vm_area_struct *vma;
1156                unsigned int foll_flags;
1157
1158                vma = find_extend_vma(mm, start);
1159                if (!vma && in_gate_area(tsk, start)) {
1160                        unsigned long pg = start & PAGE_MASK;
1161                        struct vm_area_struct *gate_vma = get_gate_vma(tsk);
1162                        pgd_t *pgd;
1163                        pud_t *pud;
1164                        pmd_t *pmd;
1165                        pte_t *pte;
1166
1167                        /* user gate pages are read-only */
1168                        if (!ignore && write)
1169                                return i ? : -EFAULT;
1170                        if (pg > TASK_SIZE)
1171                                pgd = pgd_offset_k(pg);
1172                        else
1173                                pgd = pgd_offset_gate(mm, pg);
1174                        BUG_ON(pgd_none(*pgd));
1175                        pud = pud_offset(pgd, pg);
1176                        BUG_ON(pud_none(*pud));
1177                        pmd = pmd_offset(pud, pg);
1178                        if (pmd_none(*pmd))
1179                                return i ? : -EFAULT;
1180                        pte = pte_offset_map(pmd, pg);
1181                        if (pte_none(*pte)) {
1182                                pte_unmap(pte);
1183                                return i ? : -EFAULT;
1184                        }
1185                        if (pages) {
1186                                struct page *page = vm_normal_page(gate_vma, start, *pte);
1187                                pages[i] = page;
1188                                if (page)
1189                                        get_page(page);
1190                        }
1191                        pte_unmap(pte);
1192                        if (vmas)
1193                                vmas[i] = gate_vma;
1194                        i++;
1195                        start += PAGE_SIZE;
1196                        len--;
1197                        continue;
1198                }
1199
1200                if (!vma ||
1201                    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1202                    (!ignore && !(vm_flags & vma->vm_flags)))
1203                        return i ? : -EFAULT;
1204
1205                if (is_vm_hugetlb_page(vma)) {
1206                        i = follow_hugetlb_page(mm, vma, pages, vmas,
1207                                                &start, &len, i, write);
1208                        continue;
1209                }
1210
1211                foll_flags = FOLL_TOUCH;
1212                if (pages)
1213                        foll_flags |= FOLL_GET;
1214                if (!write && use_zero_page(vma))
1215                        foll_flags |= FOLL_ANON;
1216
1217                do {
1218                        struct page *page;
1219
1220                        /*
1221                         * If tsk is ooming, cut off its access to large memory
1222                         * allocations. It has a pending SIGKILL, but it can't
1223                         * be processed until returning to user space.
1224                         */
1225                        if (unlikely(test_tsk_thread_flag(tsk, TIF_MEMDIE)))
1226                                return i ? i : -ENOMEM;
1227
1228                        if (write)
1229                                foll_flags |= FOLL_WRITE;
1230
1231                        cond_resched();
1232                        while (!(page = follow_page(vma, start, foll_flags))) {
1233                                int ret;
1234                                ret = handle_mm_fault(mm, vma, start,
1235                                                foll_flags & FOLL_WRITE);
1236                                if (ret & VM_FAULT_ERROR) {
1237                                        if (ret & VM_FAULT_OOM)
1238                                                return i ? i : -ENOMEM;
1239                                        else if (ret & VM_FAULT_SIGBUS)
1240                                                return i ? i : -EFAULT;
1241                                        BUG();
1242                                }
1243                                if (ret & VM_FAULT_MAJOR)
1244                                        tsk->maj_flt++;
1245                                else
1246                                        tsk->min_flt++;
1247
1248                                /*
1249                                 * The VM_FAULT_WRITE bit tells us that
1250                                 * do_wp_page has broken COW when necessary,
1251                                 * even if maybe_mkwrite decided not to set
1252                                 * pte_write. We can thus safely do subsequent
1253                                 * page lookups as if they were reads.
1254                                 */
1255                                if (ret & VM_FAULT_WRITE)
1256                                        foll_flags &= ~FOLL_WRITE;
1257
1258                                cond_resched();
1259                        }
1260                        if (IS_ERR(page))
1261                                return i ? i : PTR_ERR(page);
1262                        if (pages) {
1263                                pages[i] = page;
1264
1265                                flush_anon_page(vma, page, start);
1266                                flush_dcache_page(page);
1267                        }
1268                        if (vmas)
1269                                vmas[i] = vma;
1270                        i++;
1271                        start += PAGE_SIZE;
1272                        len--;
1273                } while (len && start < vma->vm_end);
1274        } while (len);
1275        return i;
1276}
1277
1278int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1279                unsigned long start, int len, int write, int force,
1280                struct page **pages, struct vm_area_struct **vmas)
1281{
1282        int flags = 0;
1283
1284        if (write)
1285                flags |= GUP_FLAGS_WRITE;
1286        if (force)
1287                flags |= GUP_FLAGS_FORCE;
1288
1289        return __get_user_pages(tsk, mm,
1290                                start, len, flags,
1291                                pages, vmas);
1292}
1293
1294EXPORT_SYMBOL(get_user_pages);
1295
1296pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
1297                        spinlock_t **ptl)
1298{
1299        pgd_t * pgd = pgd_offset(mm, addr);
1300        pud_t * pud = pud_alloc(mm, pgd, addr);
1301        if (pud) {
1302                pmd_t * pmd = pmd_alloc(mm, pud, addr);
1303                if (pmd)
1304                        return pte_alloc_map_lock(mm, pmd, addr, ptl);
1305        }
1306        return NULL;
1307}
1308
1309/*
1310 * This is the old fallback for page remapping.
1311 *
1312 * For historical reasons, it only allows reserved pages. Only
1313 * old drivers should use this, and they needed to mark their
1314 * pages reserved for the old functions anyway.
1315 */
1316static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1317                        struct page *page, pgprot_t prot)
1318{
1319        struct mm_struct *mm = vma->vm_mm;
1320        int retval;
1321        pte_t *pte;
1322        spinlock_t *ptl;
1323
1324        retval = -EINVAL;
1325        if (PageAnon(page))
1326                goto out;
1327        retval = -ENOMEM;
1328        flush_dcache_page(page);
1329        pte = get_locked_pte(mm, addr, &ptl);
1330        if (!pte)
1331                goto out;
1332        retval = -EBUSY;
1333        if (!pte_none(*pte))
1334                goto out_unlock;
1335
1336        /* Ok, finally just insert the thing.. */
1337        get_page(page);
1338        inc_mm_counter(mm, file_rss);
1339        page_add_file_rmap(page);
1340        set_pte_at(mm, addr, pte, mk_pte(page, prot));
1341
1342        retval = 0;
1343        pte_unmap_unlock(pte, ptl);
1344        return retval;
1345out_unlock:
1346        pte_unmap_unlock(pte, ptl);
1347out:
1348        return retval;
1349}
1350
1351/**
1352 * vm_insert_page - insert single page into user vma
1353 * @vma: user vma to map to
1354 * @addr: target user address of this page
1355 * @page: source kernel page
1356 *
1357 * This allows drivers to insert individual pages they've allocated
1358 * into a user vma.
1359 *
1360 * The page has to be a nice clean _individual_ kernel allocation.
1361 * If you allocate a compound page, you need to have marked it as
1362 * such (__GFP_COMP), or manually just split the page up yourself
1363 * (see split_page()).
1364 *
1365 * NOTE! Traditionally this was done with "remap_pfn_range()" which
1366 * took an arbitrary page protection parameter. This doesn't allow
1367 * that. Your vma protection will have to be set up correctly, which
1368 * means that if you want a shared writable mapping, you'd better
1369 * ask for a shared writable mapping!
1370 *
1371 * The page does not need to be reserved.
1372 */
1373int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1374                        struct page *page)
1375{
1376        if (addr < vma->vm_start || addr >= vma->vm_end)
1377                return -EFAULT;
1378        if (!page_count(page))
1379                return -EINVAL;
1380        vma->vm_flags |= VM_INSERTPAGE;
1381        return insert_page(vma, addr, page, vma->vm_page_prot);
1382}
1383EXPORT_SYMBOL(vm_insert_page);
1384
1385static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1386                        unsigned long pfn, pgprot_t prot)
1387{
1388        struct mm_struct *mm = vma->vm_mm;
1389        int retval;
1390        pte_t *pte, entry;
1391        spinlock_t *ptl;
1392
1393        retval = -ENOMEM;
1394        pte = get_locked_pte(mm, addr, &ptl);
1395        if (!pte)
1396                goto out;
1397        retval = -EBUSY;
1398        if (!pte_none(*pte))
1399                goto out_unlock;
1400
1401        /* Ok, finally just insert the thing.. */
1402        entry = pte_mkspecial(pfn_pte(pfn, prot));
1403        set_pte_at(mm, addr, pte, entry);
1404        update_mmu_cache(vma, addr, entry); /* XXX: why not for insert_page? */
1405
1406        retval = 0;
1407out_unlock:
1408        pte_unmap_unlock(pte, ptl);
1409out:
1410        return retval;
1411}
1412
1413/**
1414 * vm_insert_pfn - insert single pfn into user vma
1415 * @vma: user vma to map to
1416 * @addr: target user address of this page
1417 * @pfn: source kernel pfn
1418 *
1419 * Similar to vm_inert_page, this allows drivers to insert individual pages
1420 * they've allocated into a user vma. Same comments apply.
1421 *
1422 * This function should only be called from a vm_ops->fault handler, and
1423 * in that case the handler should return NULL.
1424 *
1425 * vma cannot be a COW mapping.
1426 *
1427 * As this is called only for pages that do not currently exist, we
1428 * do not need to flush old virtual caches or the TLB.
1429 */
1430int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1431                        unsigned long pfn)
1432{
1433        /*
1434         * Technically, architectures with pte_special can avoid all these
1435         * restrictions (same for remap_pfn_range).  However we would like
1436         * consistency in testing and feature parity among all, so we should
1437         * try to keep these invariants in place for everybody.
1438         */
1439        BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1440        BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1441                                                (VM_PFNMAP|VM_MIXEDMAP));
1442        BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1443        BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1444
1445        if (addr < vma->vm_start || addr >= vma->vm_end)
1446                return -EFAULT;
1447        return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1448}
1449EXPORT_SYMBOL(vm_insert_pfn);
1450
1451int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1452                        unsigned long pfn)
1453{
1454        BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1455
1456        if (addr < vma->vm_start || addr >= vma->vm_end)
1457                return -EFAULT;
1458
1459        /*
1460         * If we don't have pte special, then we have to use the pfn_valid()
1461         * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1462         * refcount the page if pfn_valid is true (hence insert_page rather
1463         * than insert_pfn).
1464         */
1465        if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1466                struct page *page;
1467
1468                page = pfn_to_page(pfn);
1469                return insert_page(vma, addr, page, vma->vm_page_prot);
1470        }
1471        return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1472}
1473EXPORT_SYMBOL(vm_insert_mixed);
1474
1475/*
1476 * maps a range of physical memory into the requested pages. the old
1477 * mappings are removed. any references to nonexistent pages results
1478 * in null mappings (currently treated as "copy-on-access")
1479 */
1480static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1481                        unsigned long addr, unsigned long end,
1482                        unsigned long pfn, pgprot_t prot)
1483{
1484        pte_t *pte;
1485        spinlock_t *ptl;
1486
1487        pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1488        if (!pte)
1489                return -ENOMEM;
1490        arch_enter_lazy_mmu_mode();
1491        do {
1492                BUG_ON(!pte_none(*pte));
1493                set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1494                pfn++;
1495        } while (pte++, addr += PAGE_SIZE, addr != end);
1496        arch_leave_lazy_mmu_mode();
1497        pte_unmap_unlock(pte - 1, ptl);
1498        return 0;
1499}
1500
1501static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1502                        unsigned long addr, unsigned long end,
1503                        unsigned long pfn, pgprot_t prot)
1504{
1505        pmd_t *pmd;
1506        unsigned long next;
1507
1508        pfn -= addr >> PAGE_SHIFT;
1509        pmd = pmd_alloc(mm, pud, addr);
1510        if (!pmd)
1511                return -ENOMEM;
1512        do {
1513                next = pmd_addr_end(addr, end);
1514                if (remap_pte_range(mm, pmd, addr, next,
1515                                pfn + (addr >> PAGE_SHIFT), prot))
1516                        return -ENOMEM;
1517        } while (pmd++, addr = next, addr != end);
1518        return 0;
1519}
1520
1521static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1522                        unsigned long addr, unsigned long end,
1523                        unsigned long pfn, pgprot_t prot)
1524{
1525        pud_t *pud;
1526        unsigned long next;
1527
1528        pfn -= addr >> PAGE_SHIFT;
1529        pud = pud_alloc(mm, pgd, addr);
1530        if (!pud)
1531                return -ENOMEM;
1532        do {
1533                next = pud_addr_end(addr, end);
1534                if (remap_pmd_range(mm, pud, addr, next,
1535                                pfn + (addr >> PAGE_SHIFT), prot))
1536                        return -ENOMEM;
1537        } while (pud++, addr = next, addr != end);
1538        return 0;
1539}
1540
1541/**
1542 * remap_pfn_range - remap kernel memory to userspace
1543 * @vma: user vma to map to
1544 * @addr: target user address to start at
1545 * @pfn: physical address of kernel memory
1546 * @size: size of map area
1547 * @prot: page protection flags for this mapping
1548 *
1549 *  Note: this is only safe if the mm semaphore is held when called.
1550 */
1551int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1552                    unsigned long pfn, unsigned long size, pgprot_t prot)
1553{
1554        pgd_t *pgd;
1555        unsigned long next;
1556        unsigned long end = addr + PAGE_ALIGN(size);
1557        struct mm_struct *mm = vma->vm_mm;
1558        int err;
1559
1560        /*
1561         * Physically remapped pages are special. Tell the
1562         * rest of the world about it:
1563         *   VM_IO tells people not to look at these pages
1564         *      (accesses can have side effects).
1565         *   VM_RESERVED is specified all over the place, because
1566         *      in 2.4 it kept swapout's vma scan off this vma; but
1567         *      in 2.6 the LRU scan won't even find its pages, so this
1568         *      flag means no more than count its pages in reserved_vm,
1569         *      and omit it from core dump, even when VM_IO turned off.
1570         *   VM_PFNMAP tells the core MM that the base pages are just
1571         *      raw PFN mappings, and do not have a "struct page" associated
1572         *      with them.
1573         *
1574         * There's a horrible special case to handle copy-on-write
1575         * behaviour that some programs depend on. We mark the "original"
1576         * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1577         */
1578        if (is_cow_mapping(vma->vm_flags)) {
1579                if (addr != vma->vm_start || end != vma->vm_end)
1580                        return -EINVAL;
1581                vma->vm_pgoff = pfn;
1582        }
1583
1584        vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1585
1586        BUG_ON(addr >= end);
1587        pfn -= addr >> PAGE_SHIFT;
1588        pgd = pgd_offset(mm, addr);
1589        flush_cache_range(vma, addr, end);
1590        do {
1591                next = pgd_addr_end(addr, end);
1592                err = remap_pud_range(mm, pgd, addr, next,
1593                                pfn + (addr >> PAGE_SHIFT), prot);
1594                if (err)
1595                        break;
1596        } while (pgd++, addr = next, addr != end);
1597        return err;
1598}
1599EXPORT_SYMBOL(remap_pfn_range);
1600
1601static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1602                                     unsigned long addr, unsigned long end,
1603                                     pte_fn_t fn, void *data)
1604{
1605        pte_t *pte;
1606        int err;
1607        pgtable_t token;
1608        spinlock_t *uninitialized_var(ptl);
1609
1610        pte = (mm == &init_mm) ?
1611                pte_alloc_kernel(pmd, addr) :
1612                pte_alloc_map_lock(mm, pmd, addr, &ptl);
1613        if (!pte)
1614                return -ENOMEM;
1615
1616        BUG_ON(pmd_huge(*pmd));
1617
1618        token = pmd_pgtable(*pmd);
1619
1620        do {
1621                err = fn(pte, token, addr, data);
1622                if (err)
1623                        break;
1624        } while (pte++, addr += PAGE_SIZE, addr != end);
1625
1626        if (mm != &init_mm)
1627                pte_unmap_unlock(pte-1, ptl);
1628        return err;
1629}
1630
1631static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1632                                     unsigned long addr, unsigned long end,
1633                                     pte_fn_t fn, void *data)
1634{
1635        pmd_t *pmd;
1636        unsigned long next;
1637        int err;
1638
1639        BUG_ON(pud_huge(*pud));
1640
1641        pmd = pmd_alloc(mm, pud, addr);
1642        if (!pmd)
1643                return -ENOMEM;
1644        do {
1645                next = pmd_addr_end(addr, end);
1646                err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1647                if (err)
1648                        break;
1649        } while (pmd++, addr = next, addr != end);
1650        return err;
1651}
1652
1653static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1654                                     unsigned long addr, unsigned long end,
1655                                     pte_fn_t fn, void *data)
1656{
1657        pud_t *pud;
1658        unsigned long next;
1659        int err;
1660
1661        pud = pud_alloc(mm, pgd, addr);
1662        if (!pud)
1663                return -ENOMEM;
1664        do {
1665                next = pud_addr_end(addr, end);
1666                err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1667                if (err)
1668                        break;
1669        } while (pud++, addr = next, addr != end);
1670        return err;
1671}
1672
1673/*
1674 * Scan a region of virtual memory, filling in page tables as necessary
1675 * and calling a provided function on each leaf page table.
1676 */
1677int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1678                        unsigned long size, pte_fn_t fn, void *data)
1679{
1680        pgd_t *pgd;
1681        unsigned long next;
1682        unsigned long start = addr, end = addr + size;
1683        int err;
1684
1685        BUG_ON(addr >= end);
1686        mmu_notifier_invalidate_range_start(mm, start, end);
1687        pgd = pgd_offset(mm, addr);
1688        do {
1689                next = pgd_addr_end(addr, end);
1690                err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1691                if (err)
1692                        break;
1693        } while (pgd++, addr = next, addr != end);
1694        mmu_notifier_invalidate_range_end(mm, start, end);
1695        return err;
1696}
1697EXPORT_SYMBOL_GPL(apply_to_page_range);
1698
1699/*
1700 * handle_pte_fault chooses page fault handler according to an entry
1701 * which was read non-atomically.  Before making any commitment, on
1702 * those architectures or configurations (e.g. i386 with PAE) which
1703 * might give a mix of unmatched parts, do_swap_page and do_file_page
1704 * must check under lock before unmapping the pte and proceeding
1705 * (but do_wp_page is only called after already making such a check;
1706 * and do_anonymous_page and do_no_page can safely check later on).
1707 */
1708static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1709                                pte_t *page_table, pte_t orig_pte)
1710{
1711        int same = 1;
1712#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1713        if (sizeof(pte_t) > sizeof(unsigned long)) {
1714                spinlock_t *ptl = pte_lockptr(mm, pmd);
1715                spin_lock(ptl);
1716                same = pte_same(*page_table, orig_pte);
1717                spin_unlock(ptl);
1718        }
1719#endif
1720        pte_unmap(page_table);
1721        return same;
1722}
1723
1724/*
1725 * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
1726 * servicing faults for write access.  In the normal case, do always want
1727 * pte_mkwrite.  But get_user_pages can cause write faults for mappings
1728 * that do not have writing enabled, when used by access_process_vm.
1729 */
1730static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
1731{
1732        if (likely(vma->vm_flags & VM_WRITE))
1733                pte = pte_mkwrite(pte);
1734        return pte;
1735}
1736
1737static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1738{
1739        /*
1740         * If the source page was a PFN mapping, we don't have
1741         * a "struct page" for it. We do a best-effort copy by
1742         * just copying from the original user address. If that
1743         * fails, we just zero-fill it. Live with it.
1744         */
1745        if (unlikely(!src)) {
1746                void *kaddr = kmap_atomic(dst, KM_USER0);
1747                void __user *uaddr = (void __user *)(va & PAGE_MASK);
1748
1749                /*
1750                 * This really shouldn't fail, because the page is there
1751                 * in the page tables. But it might just be unreadable,
1752                 * in which case we just give up and fill the result with
1753                 * zeroes.
1754                 */
1755                if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
1756                        memset(kaddr, 0, PAGE_SIZE);
1757                kunmap_atomic(kaddr, KM_USER0);
1758                flush_dcache_page(dst);
1759        } else
1760                copy_user_highpage(dst, src, va, vma);
1761}
1762
1763/*
1764 * This routine handles present pages, when users try to write
1765 * to a shared page. It is done by copying the page to a new address
1766 * and decrementing the shared-page counter for the old page.
1767 *
1768 * Note that this routine assumes that the protection checks have been
1769 * done by the caller (the low-level page fault routine in most cases).
1770 * Thus we can safely just mark it writable once we've done any necessary
1771 * COW.
1772 *
1773 * We also mark the page dirty at this point even though the page will
1774 * change only once the write actually happens. This avoids a few races,
1775 * and potentially makes it more efficient.
1776 *
1777 * We enter with non-exclusive mmap_sem (to exclude vma changes,
1778 * but allow concurrent faults), with pte both mapped and locked.
1779 * We return with mmap_sem still held, but pte unmapped and unlocked.
1780 */
1781static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1782                unsigned long address, pte_t *page_table, pmd_t *pmd,
1783                spinlock_t *ptl, pte_t orig_pte)
1784{
1785        struct page *old_page, *new_page;
1786        pte_t entry;
1787        int reuse = 0, ret = 0;
1788        int page_mkwrite = 0;
1789        struct page *dirty_page = NULL;
1790
1791        old_page = vm_normal_page(vma, address, orig_pte);
1792        if (!old_page) {
1793                /*
1794                 * VM_MIXEDMAP !pfn_valid() case
1795                 *
1796                 * We should not cow pages in a shared writeable mapping.
1797                 * Just mark the pages writable as we can't do any dirty
1798                 * accounting on raw pfn maps.
1799                 */
1800                if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
1801                                     (VM_WRITE|VM_SHARED))
1802                        goto reuse;
1803                goto gotten;
1804        }
1805
1806        /*
1807         * Take out anonymous pages first, anonymous shared vmas are
1808         * not dirty accountable.
1809         */
1810        if (PageAnon(old_page)) {
1811                if (trylock_page(old_page)) {
1812                        reuse = can_share_swap_page(old_page);
1813                        unlock_page(old_page);
1814                }
1815        } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
1816                                        (VM_WRITE|VM_SHARED))) {
1817                /*
1818                 * Only catch write-faults on shared writable pages,
1819                 * read-only shared pages can get COWed by
1820                 * get_user_pages(.write=1, .force=1).
1821                 */
1822                if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
1823                        /*
1824                         * Notify the address space that the page is about to
1825                         * become writable so that it can prohibit this or wait
1826                         * for the page to get into an appropriate state.
1827                         *
1828                         * We do this without the lock held, so that it can
1829                         * sleep if it needs to.
1830                         */
1831                        page_cache_get(old_page);
1832                        pte_unmap_unlock(page_table, ptl);
1833
1834                        if (vma->vm_ops->page_mkwrite(vma, old_page) < 0)
1835                                goto unwritable_page;
1836
1837                        /*
1838                         * Since we dropped the lock we need to revalidate
1839                         * the PTE as someone else may have changed it.  If
1840                         * they did, we just return, as we can count on the
1841                         * MMU to tell us if they didn't also make it writable.
1842                         */
1843                        page_table = pte_offset_map_lock(mm, pmd, address,
1844                                                         &ptl);
1845                        page_cache_release(old_page);
1846                        if (!pte_same(*page_table, orig_pte))
1847                                goto unlock;
1848
1849                        page_mkwrite = 1;
1850                }
1851                dirty_page = old_page;
1852                get_page(dirty_page);
1853                reuse = 1;
1854        }
1855
1856        if (reuse) {
1857reuse:
1858                flush_cache_page(vma, address, pte_pfn(orig_pte));
1859                entry = pte_mkyoung(orig_pte);
1860                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1861                if (ptep_set_access_flags(vma, address, page_table, entry,1))
1862                        update_mmu_cache(vma, address, entry);
1863                ret |= VM_FAULT_WRITE;
1864                goto unlock;
1865        }
1866
1867        /*
1868         * Ok, we need to copy. Oh, well..
1869         */
1870        page_cache_get(old_page);
1871gotten:
1872        pte_unmap_unlock(page_table, ptl);
1873
1874        if (unlikely(anon_vma_prepare(vma)))
1875                goto oom;
1876        VM_BUG_ON(old_page == ZERO_PAGE(0));
1877        new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
1878        if (!new_page)
1879                goto oom;
1880        /*
1881         * Don't let another task, with possibly unlocked vma,
1882         * keep the mlocked page.
1883         */
1884        if (vma->vm_flags & VM_LOCKED) {
1885                lock_page(old_page);    /* for LRU manipulation */
1886                clear_page_mlock(old_page);
1887                unlock_page(old_page);
1888        }
1889        cow_user_page(new_page, old_page, address, vma);
1890        __SetPageUptodate(new_page);
1891
1892        if (mem_cgroup_charge(new_page, mm, GFP_KERNEL))
1893                goto oom_free_new;
1894
1895        /*
1896         * Re-check the pte - we dropped the lock
1897         */
1898        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1899        if (likely(pte_same(*page_table, orig_pte))) {
1900                if (old_page) {
1901                        if (!PageAnon(old_page)) {
1902                                dec_mm_counter(mm, file_rss);
1903                                inc_mm_counter(mm, anon_rss);
1904                        }
1905                } else
1906                        inc_mm_counter(mm, anon_rss);
1907                flush_cache_page(vma, address, pte_pfn(orig_pte));
1908                entry = mk_pte(new_page, vma->vm_page_prot);
1909                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1910                /*
1911                 * Clear the pte entry and flush it first, before updating the
1912                 * pte with the new entry. This will avoid a race condition
1913                 * seen in the presence of one thread doing SMC and another
1914                 * thread doing COW.
1915                 */
1916                ptep_clear_flush_notify(vma, address, page_table);
1917                SetPageSwapBacked(new_page);
1918                lru_cache_add_active_or_unevictable(new_page, vma);
1919                page_add_new_anon_rmap(new_page, vma, address);
1920
1921//TODO:  is this safe?  do_anonymous_page() does it this way.
1922                set_pte_at(mm, address, page_table, entry);
1923                update_mmu_cache(vma, address, entry);
1924                if (old_page) {
1925                        /*
1926                         * Only after switching the pte to the new page may
1927                         * we remove the mapcount here. Otherwise another
1928                         * process may come and find the rmap count decremented
1929                         * before the pte is switched to the new page, and
1930                         * "reuse" the old page writing into it while our pte
1931                         * here still points into it and can be read by other
1932                         * threads.
1933                         *
1934                         * The critical issue is to order this
1935                         * page_remove_rmap with the ptp_clear_flush above.
1936                         * Those stores are ordered by (if nothing else,)
1937                         * the barrier present in the atomic_add_negative
1938                         * in page_remove_rmap.
1939                         *
1940                         * Then the TLB flush in ptep_clear_flush ensures that
1941                         * no process can access the old page before the
1942                         * decremented mapcount is visible. And the old page
1943                         * cannot be reused until after the decremented
1944                         * mapcount is visible. So transitively, TLBs to
1945                         * old page will be flushed before it can be reused.
1946                         */
1947                        page_remove_rmap(old_page, vma);
1948                }
1949
1950                /* Free the old page.. */
1951                new_page = old_page;
1952                ret |= VM_FAULT_WRITE;
1953        } else
1954                mem_cgroup_uncharge_page(new_page);
1955
1956        if (new_page)
1957                page_cache_release(new_page);
1958        if (old_page)
1959                page_cache_release(old_page);
1960unlock:
1961        pte_unmap_unlock(page_table, ptl);
1962        if (dirty_page) {
1963                if (vma->vm_file)
1964                        file_update_time(vma->vm_file);
1965
1966                /*
1967                 * Yes, Virginia, this is actually required to prevent a race
1968                 * with clear_page_dirty_for_io() from clearing the page dirty
1969                 * bit after it clear all dirty ptes, but before a racing
1970                 * do_wp_page installs a dirty pte.
1971                 *
1972                 * do_no_page is protected similarly.
1973                 */
1974                wait_on_page_locked(dirty_page);
1975                set_page_dirty_balance(dirty_page, page_mkwrite);
1976                put_page(dirty_page);
1977        }
1978        return ret;
1979oom_free_new:
1980        page_cache_release(new_page);
1981oom:
1982        if (old_page)
1983                page_cache_release(old_page);
1984        return VM_FAULT_OOM;
1985
1986unwritable_page:
1987        page_cache_release(old_page);
1988        return VM_FAULT_SIGBUS;
1989}
1990
1991/*
1992 * Helper functions for unmap_mapping_range().
1993 *
1994 * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
1995 *
1996 * We have to restart searching the prio_tree whenever we drop the lock,
1997 * since the iterator is only valid while the lock is held, and anyway
1998 * a later vma might be split and reinserted earlier while lock dropped.
1999 *
2000 * The list of nonlinear vmas could be handled more efficiently, using
2001 * a placeholder, but handle it in the same way until a need is shown.
2002 * It is important to search the prio_tree before nonlinear list: a vma
2003 * may become nonlinear and be shifted from prio_tree to nonlinear list
2004 * while the lock is dropped; but never shifted from list to prio_tree.
2005 *
2006 * In order to make forward progress despite restarting the search,
2007 * vm_truncate_count is used to mark a vma as now dealt with, so we can
2008 * quickly skip it next time around.  Since the prio_tree search only
2009 * shows us those vmas affected by unmapping the range in question, we
2010 * can't efficiently keep all vmas in step with mapping->truncate_count:
2011 * so instead reset them all whenever it wraps back to 0 (then go to 1).
2012 * mapping->truncate_count and vma->vm_truncate_count are protected by
2013 * i_mmap_lock.
2014 *
2015 * In order to make forward progress despite repeatedly restarting some
2016 * large vma, note the restart_addr from unmap_vmas when it breaks out:
2017 * and restart from that address when we reach that vma again.  It might
2018 * have been split or merged, shrunk or extended, but never shifted: so
2019 * restart_addr remains valid so long as it remains in the vma's range.
2020 * unmap_mapping_range forces truncate_count to leap over page-aligned
2021 * values so we can save vma's restart_addr in its truncate_count field.
2022 */
2023#define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
2024
2025static void reset_vma_truncate_counts(struct address_space *mapping)
2026{
2027        struct vm_area_struct *vma;
2028        struct prio_tree_iter iter;
2029
2030        vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
2031                vma->vm_truncate_count = 0;
2032        list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
2033                vma->vm_truncate_count = 0;
2034}
2035
2036static int unmap_mapping_range_vma(struct vm_area_struct *vma,
2037                unsigned long start_addr, unsigned long end_addr,
2038                struct zap_details *details)
2039{
2040        unsigned long restart_addr;
2041        int need_break;
2042
2043        /*
2044         * files that support invalidating or truncating portions of the
2045         * file from under mmaped areas must have their ->fault function
2046         * return a locked page (and set VM_FAULT_LOCKED in the return).
2047         * This provides synchronisation against concurrent unmapping here.
2048         */
2049
2050again:
2051        restart_addr = vma->vm_truncate_count;
2052        if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
2053                start_addr = restart_addr;
2054                if (start_addr >= end_addr) {
2055                        /* Top of vma has been split off since last time */
2056                        vma->vm_truncate_count = details->truncate_count;
2057                        return 0;
2058                }
2059        }
2060
2061        restart_addr = zap_page_range(vma, start_addr,
2062                                        end_addr - start_addr, details);
2063        need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
2064
2065        if (restart_addr >= end_addr) {
2066                /* We have now completed this vma: mark it so */
2067                vma->vm_truncate_count = details->truncate_count;
2068                if (!need_break)
2069                        return 0;
2070        } else {
2071                /* Note restart_addr in vma's truncate_count field */
2072                vma->vm_truncate_count = restart_addr;
2073                if (!need_break)
2074                        goto again;
2075        }
2076
2077        spin_unlock(details->i_mmap_lock);
2078        cond_resched();
2079        spin_lock(details->i_mmap_lock);
2080        return -EINTR;
2081}
2082
2083static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
2084                                            struct zap_details *details)
2085{
2086        struct vm_area_struct *vma;
2087        struct prio_tree_iter iter;
2088        pgoff_t vba, vea, zba, zea;
2089
2090restart:
2091        vma_prio_tree_foreach(vma, &iter, root,
2092                        details->first_index, details->last_index) {
2093                /* Skip quickly over those we have already dealt with */
2094                if (vma->vm_truncate_count == details->truncate_count)
2095                        continue;
2096
2097                vba = vma->vm_pgoff;
2098                vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2099                /* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2100                zba = details->first_index;
2101                if (zba < vba)
2102                        zba = vba;
2103                zea = details->last_index;
2104                if (zea > vea)
2105                        zea = vea;
2106
2107                if (unmap_mapping_range_vma(vma,
2108                        ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2109                        ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2110                                details) < 0)
2111                        goto restart;
2112        }
2113}
2114
2115static inline void unmap_mapping_range_list(struct list_head *head,
2116                                            struct zap_details *details)
2117{
2118        struct vm_area_struct *vma;
2119
2120        /*
2121         * In nonlinear VMAs there is no correspondence between virtual address
2122         * offset and file offset.  So we must perform an exhaustive search
2123         * across *all* the pages in each nonlinear VMA, not just the pages
2124         * whose virtual address lies outside the file truncation point.
2125         */
2126restart:
2127        list_for_each_entry(vma, head, shared.vm_set.list) {
2128                /* Skip quickly over those we have already dealt with */
2129                if (vma->vm_truncate_count == details->truncate_count)
2130                        continue;
2131                details->nonlinear_vma = vma;
2132                if (unmap_mapping_range_vma(vma, vma->vm_start,
2133                                        vma->vm_end, details) < 0)
2134                        goto restart;
2135        }
2136}
2137
2138/**
2139 * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2140 * @mapping: the address space containing mmaps to be unmapped.
2141 * @holebegin: byte in first page to unmap, relative to the start of
2142 * the underlying file.  This will be rounded down to a PAGE_SIZE
2143 * boundary.  Note that this is different from vmtruncate(), which
2144 * must keep the partial page.  In contrast, we must get rid of
2145 * partial pages.
2146 * @holelen: size of prospective hole in bytes.  This will be rounded
2147 * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2148 * end of the file.
2149 * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2150 * but 0 when invalidating pagecache, don't throw away private data.
2151 */
2152void unmap_mapping_range(struct address_space *mapping,
2153                loff_t const holebegin, loff_t const holelen, int even_cows)
2154{
2155        struct zap_details details;
2156        pgoff_t hba = holebegin >> PAGE_SHIFT;
2157        pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2158
2159        /* Check for overflow. */
2160        if (sizeof(holelen) > sizeof(hlen)) {
2161                long long holeend =
2162                        (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2163                if (holeend & ~(long long)ULONG_MAX)
2164                        hlen = ULONG_MAX - hba + 1;
2165        }
2166
2167        details.check_mapping = even_cows? NULL: mapping;
2168        details.nonlinear_vma = NULL;
2169        details.first_index = hba;
2170        details.last_index = hba + hlen - 1;
2171        if (details.last_index < details.first_index)
2172                details.last_index = ULONG_MAX;
2173        details.i_mmap_lock = &mapping->i_mmap_lock;
2174
2175        spin_lock(&mapping->i_mmap_lock);
2176
2177        /* Protect against endless unmapping loops */
2178        mapping->truncate_count++;
2179        if (unlikely(is_restart_addr(mapping->truncate_count))) {
2180                if (mapping->truncate_count == 0)
2181                        reset_vma_truncate_counts(mapping);
2182                mapping->truncate_count++;
2183        }
2184        details.truncate_count = mapping->truncate_count;
2185
2186        if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
2187                unmap_mapping_range_tree(&mapping->i_mmap, &details);
2188        if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2189                unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2190        spin_unlock(&mapping->i_mmap_lock);
2191}
2192EXPORT_SYMBOL(unmap_mapping_range);
2193
2194/**
2195 * vmtruncate - unmap mappings "freed" by truncate() syscall
2196 * @inode: inode of the file used
2197 * @offset: file offset to start truncating
2198 *
2199 * NOTE! We have to be ready to update the memory sharing
2200 * between the file and the memory map for a potential last
2201 * incomplete page.  Ugly, but necessary.
2202 */
2203int vmtruncate(struct inode * inode, loff_t offset)
2204{
2205        if (inode->i_size < offset) {
2206                unsigned long limit;
2207
2208                limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2209                if (limit != RLIM_INFINITY && offset > limit)
2210                        goto out_sig;
2211                if (offset > inode->i_sb->s_maxbytes)
2212                        goto out_big;
2213                i_size_write(inode, offset);
2214        } else {
2215                struct address_space *mapping = inode->i_mapping;
2216
2217                /*
2218                 * truncation of in-use swapfiles is disallowed - it would
2219                 * cause subsequent swapout to scribble on the now-freed
2220                 * blocks.
2221                 */
2222                if (IS_SWAPFILE(inode))
2223                        return -ETXTBSY;
2224                i_size_write(inode, offset);
2225
2226                /*
2227                 * unmap_mapping_range is called twice, first simply for
2228                 * efficiency so that truncate_inode_pages does fewer
2229                 * single-page unmaps.  However after this first call, and
2230                 * before truncate_inode_pages finishes, it is possible for
2231                 * private pages to be COWed, which remain after
2232                 * truncate_inode_pages finishes, hence the second
2233                 * unmap_mapping_range call must be made for correctness.
2234                 */
2235                unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
2236                truncate_inode_pages(mapping, offset);
2237                unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
2238        }
2239
2240        if (inode->i_op && inode->i_op->truncate)
2241                inode->i_op->truncate(inode);
2242        return 0;
2243
2244out_sig:
2245        send_sig(SIGXFSZ, current, 0);
2246out_big:
2247        return -EFBIG;
2248}
2249EXPORT_SYMBOL(vmtruncate);
2250
2251int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
2252{
2253        struct address_space *mapping = inode->i_mapping;
2254
2255        /*
2256         * If the underlying filesystem is not going to provide
2257         * a way to truncate a range of blocks (punch a hole) -
2258         * we should return failure right now.
2259         */
2260        if (!inode->i_op || !inode->i_op->truncate_range)
2261                return -ENOSYS;
2262
2263        mutex_lock(&inode->i_mutex);
2264        down_write(&inode->i_alloc_sem);
2265        unmap_mapping_range(mapping, offset, (end - offset), 1);
2266        truncate_inode_pages_range(mapping, offset, end);
2267        unmap_mapping_range(mapping, offset, (end - offset), 1);
2268        inode->i_op->truncate_range(inode, offset, end);
2269        up_write(&inode->i_alloc_sem);
2270        mutex_unlock(&inode->i_mutex);
2271
2272        return 0;
2273}
2274
2275/*
2276 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2277 * but allow concurrent faults), and pte mapped but not yet locked.
2278 * We return with mmap_sem still held, but pte unmapped and unlocked.
2279 */
2280static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2281                unsigned long address, pte_t *page_table, pmd_t *pmd,
2282                int write_access, pte_t orig_pte)
2283{
2284        spinlock_t *ptl;
2285        struct page *page;
2286        swp_entry_t entry;
2287        pte_t pte;
2288        int ret = 0;
2289
2290        if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2291                goto out;
2292
2293        entry = pte_to_swp_entry(orig_pte);
2294        if (is_migration_entry(entry)) {
2295                migration_entry_wait(mm, pmd, address);
2296                goto out;
2297        }
2298        delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2299        page = lookup_swap_cache(entry);
2300        if (!page) {
2301                grab_swap_token(); /* Contend for token _before_ read-in */
2302                page = swapin_readahead(entry,
2303                                        GFP_HIGHUSER_MOVABLE, vma, address);
2304                if (!page) {
2305                        /*
2306                         * Back out if somebody else faulted in this pte
2307                         * while we released the pte lock.
2308                         */
2309                        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2310                        if (likely(pte_same(*page_table, orig_pte)))
2311                                ret = VM_FAULT_OOM;
2312                        delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2313                        goto unlock;
2314                }
2315
2316                /* Had to read the page from swap area: Major fault */
2317                ret = VM_FAULT_MAJOR;
2318                count_vm_event(PGMAJFAULT);
2319        }
2320
2321        mark_page_accessed(page);
2322
2323        lock_page(page);
2324        delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2325
2326        if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
2327                ret = VM_FAULT_OOM;
2328                unlock_page(page);
2329                goto out;
2330        }
2331
2332        /*
2333         * Back out if somebody else already faulted in this pte.
2334         */
2335        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2336        if (unlikely(!pte_same(*page_table, orig_pte)))
2337                goto out_nomap;
2338
2339        if (unlikely(!PageUptodate(page))) {
2340                ret = VM_FAULT_SIGBUS;
2341                goto out_nomap;
2342        }
2343
2344        /* The page isn't present yet, go ahead with the fault. */
2345
2346        inc_mm_counter(mm, anon_rss);
2347        pte = mk_pte(page, vma->vm_page_prot);
2348        if (write_access && can_share_swap_page(page)) {
2349                pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2350                write_access = 0;
2351        }
2352
2353        flush_icache_page(vma, page);
2354        set_pte_at(mm, address, page_table, pte);
2355        page_add_anon_rmap(page, vma, address);
2356
2357        swap_free(entry);
2358        if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2359                remove_exclusive_swap_page(page);
2360        unlock_page(page);
2361
2362        if (write_access) {
2363                ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2364                if (ret & VM_FAULT_ERROR)
2365                        ret &= VM_FAULT_ERROR;
2366                goto out;
2367        }
2368
2369        /* No need to invalidate - it was non-present before */
2370        update_mmu_cache(vma, address, pte);
2371unlock:
2372        pte_unmap_unlock(page_table, ptl);
2373out:
2374        return ret;
2375out_nomap:
2376        mem_cgroup_uncharge_page(page);
2377        pte_unmap_unlock(page_table, ptl);
2378        unlock_page(page);
2379        page_cache_release(page);
2380        return ret;
2381}
2382
2383/*
2384 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2385 * but allow concurrent faults), and pte mapped but not yet locked.
2386 * We return with mmap_sem still held, but pte unmapped and unlocked.
2387 */
2388static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2389                unsigned long address, pte_t *page_table, pmd_t *pmd,
2390                int write_access)
2391{
2392        struct page *page;
2393        spinlock_t *ptl;
2394        pte_t entry;
2395
2396        /* Allocate our own private page. */
2397        pte_unmap(page_table);
2398
2399        if (unlikely(anon_vma_prepare(vma)))
2400                goto oom;
2401        page = alloc_zeroed_user_highpage_movable(vma, address);
2402        if (!page)
2403                goto oom;
2404        __SetPageUptodate(page);
2405
2406        if (mem_cgroup_charge(page, mm, GFP_KERNEL))
2407                goto oom_free_page;
2408
2409        entry = mk_pte(page, vma->vm_page_prot);
2410        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2411
2412        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2413        if (!pte_none(*page_table))
2414                goto release;
2415        inc_mm_counter(mm, anon_rss);
2416        SetPageSwapBacked(page);
2417        lru_cache_add_active_or_unevictable(page, vma);
2418        page_add_new_anon_rmap(page, vma, address);
2419        set_pte_at(mm, address, page_table, entry);
2420
2421        /* No need to invalidate - it was non-present before */
2422        update_mmu_cache(vma, address, entry);
2423unlock:
2424        pte_unmap_unlock(page_table, ptl);
2425        return 0;
2426release:
2427        mem_cgroup_uncharge_page(page);
2428        page_cache_release(page);
2429        goto unlock;
2430oom_free_page:
2431        page_cache_release(page);
2432oom:
2433        return VM_FAULT_OOM;
2434}
2435
2436/*
2437 * __do_fault() tries to create a new page mapping. It aggressively
2438 * tries to share with existing pages, but makes a separate copy if
2439 * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
2440 * the next page fault.
2441 *
2442 * As this is called only for pages that do not currently exist, we
2443 * do not need to flush old virtual caches or the TLB.
2444 *
2445 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2446 * but allow concurrent faults), and pte neither mapped nor locked.
2447 * We return with mmap_sem still held, but pte unmapped and unlocked.
2448 */
2449static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2450                unsigned long address, pmd_t *pmd,
2451                pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2452{
2453        pte_t *page_table;
2454        spinlock_t *ptl;
2455        struct page *page;
2456        pte_t entry;
2457        int anon = 0;
2458        int charged = 0;
2459        struct page *dirty_page = NULL;
2460        struct vm_fault vmf;
2461        int ret;
2462        int page_mkwrite = 0;
2463
2464        vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2465        vmf.pgoff = pgoff;
2466        vmf.flags = flags;
2467        vmf.page = NULL;
2468
2469        ret = vma->vm_ops->fault(vma, &vmf);
2470        if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2471                return ret;
2472
2473        /*
2474         * For consistency in subsequent calls, make the faulted page always
2475         * locked.
2476         */
2477        if (unlikely(!(ret & VM_FAULT_LOCKED)))
2478                lock_page(vmf.page);
2479        else
2480                VM_BUG_ON(!PageLocked(vmf.page));
2481
2482        /*
2483         * Should we do an early C-O-W break?
2484         */
2485        page = vmf.page;
2486        if (flags & FAULT_FLAG_WRITE) {
2487                if (!(vma->vm_flags & VM_SHARED)) {
2488                        anon = 1;
2489                        if (unlikely(anon_vma_prepare(vma))) {
2490                                ret = VM_FAULT_OOM;
2491                                goto out;
2492                        }
2493                        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
2494                                                vma, address);
2495                        if (!page) {
2496                                ret = VM_FAULT_OOM;
2497                                goto out;
2498                        }
2499                        if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
2500                                ret = VM_FAULT_OOM;
2501                                page_cache_release(page);
2502                                goto out;
2503                        }
2504                        charged = 1;
2505                        /*
2506                         * Don't let another task, with possibly unlocked vma,
2507                         * keep the mlocked page.
2508                         */
2509                        if (vma->vm_flags & VM_LOCKED)
2510                                clear_page_mlock(vmf.page);
2511                        copy_user_highpage(page, vmf.page, address, vma);
2512                        __SetPageUptodate(page);
2513                } else {
2514                        /*
2515                         * If the page will be shareable, see if the backing
2516                         * address space wants to know that the page is about
2517                         * to become writable
2518                         */
2519                        if (vma->vm_ops->page_mkwrite) {
2520                                unlock_page(page);
2521                                if (vma->vm_ops->page_mkwrite(vma, page) < 0) {
2522                                        ret = VM_FAULT_SIGBUS;
2523                                        anon = 1; /* no anon but release vmf.page */
2524                                        goto out_unlocked;
2525                                }
2526                                lock_page(page);
2527                                /*
2528                                 * XXX: this is not quite right (racy vs
2529                                 * invalidate) to unlock and relock the page
2530                                 * like this, however a better fix requires
2531                                 * reworking page_mkwrite locking API, which
2532                                 * is better done later.
2533                                 */
2534                                if (!page->mapping) {
2535                                        ret = 0;
2536                                        anon = 1; /* no anon but release vmf.page */
2537                                        goto out;
2538                                }
2539                                page_mkwrite = 1;
2540                        }
2541                }
2542
2543        }
2544
2545        page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2546
2547        /*
2548         * This silly early PAGE_DIRTY setting removes a race
2549         * due to the bad i386 page protection. But it's valid
2550         * for other architectures too.
2551         *
2552         * Note that if write_access is true, we either now have
2553         * an exclusive copy of the page, or this is a shared mapping,
2554         * so we can make it writable and dirty to avoid having to
2555         * handle that later.
2556         */
2557        /* Only go through if we didn't race with anybody else... */
2558        if (likely(pte_same(*page_table, orig_pte))) {
2559                flush_icache_page(vma, page);
2560                entry = mk_pte(page, vma->vm_page_prot);
2561                if (flags & FAULT_FLAG_WRITE)
2562                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2563                if (anon) {
2564                        inc_mm_counter(mm, anon_rss);
2565                        SetPageSwapBacked(page);
2566                        lru_cache_add_active_or_unevictable(page, vma);
2567                        page_add_new_anon_rmap(page, vma, address);
2568                } else {
2569                        inc_mm_counter(mm, file_rss);
2570                        page_add_file_rmap(page);
2571                        if (flags & FAULT_FLAG_WRITE) {
2572                                dirty_page = page;
2573                                get_page(dirty_page);
2574                        }
2575                }
2576//TODO:  is this safe?  do_anonymous_page() does it this way.
2577                set_pte_at(mm, address, page_table, entry);
2578
2579                /* no need to invalidate: a not-present page won't be cached */
2580                update_mmu_cache(vma, address, entry);
2581        } else {
2582                if (charged)
2583                        mem_cgroup_uncharge_page(page);
2584                if (anon)
2585                        page_cache_release(page);
2586                else
2587                        anon = 1; /* no anon but release faulted_page */
2588        }
2589
2590        pte_unmap_unlock(page_table, ptl);
2591
2592out:
2593        unlock_page(vmf.page);
2594out_unlocked:
2595        if (anon)
2596                page_cache_release(vmf.page);
2597        else if (dirty_page) {
2598                if (vma->vm_file)
2599                        file_update_time(vma->vm_file);
2600
2601                set_page_dirty_balance(dirty_page, page_mkwrite);
2602                put_page(dirty_page);
2603        }
2604
2605        return ret;
2606}
2607
2608static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2609                unsigned long address, pte_t *page_table, pmd_t *pmd,
2610                int write_access, pte_t orig_pte)
2611{
2612        pgoff_t pgoff = (((address & PAGE_MASK)
2613                        - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2614        unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0);
2615
2616        pte_unmap(page_table);
2617        return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2618}
2619
2620/*
2621 * Fault of a previously existing named mapping. Repopulate the pte
2622 * from the encoded file_pte if possible. This enables swappable
2623 * nonlinear vmas.
2624 *
2625 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2626 * but allow concurrent faults), and pte mapped but not yet locked.
2627 * We return with mmap_sem still held, but pte unmapped and unlocked.
2628 */
2629static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2630                unsigned long address, pte_t *page_table, pmd_t *pmd,
2631                int write_access, pte_t orig_pte)
2632{
2633        unsigned int flags = FAULT_FLAG_NONLINEAR |
2634                                (write_access ? FAULT_FLAG_WRITE : 0);
2635        pgoff_t pgoff;
2636
2637        if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2638                return 0;
2639
2640        if (unlikely(!(vma->vm_flags & VM_NONLINEAR) ||
2641                        !(vma->vm_flags & VM_CAN_NONLINEAR))) {
2642                /*
2643                 * Page table corrupted: show pte and kill process.
2644                 */
2645                print_bad_pte(vma, orig_pte, address);
2646                return VM_FAULT_OOM;
2647        }
2648
2649        pgoff = pte_to_pgoff(orig_pte);
2650        return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2651}
2652
2653/*
2654 * These routines also need to handle stuff like marking pages dirty
2655 * and/or accessed for architectures that don't do it in hardware (most
2656 * RISC architectures).  The early dirtying is also good on the i386.
2657 *
2658 * There is also a hook called "update_mmu_cache()" that architectures
2659 * with external mmu caches can use to update those (ie the Sparc or
2660 * PowerPC hashed page tables that act as extended TLBs).
2661 *
2662 * We enter with non-exclusive mmap_sem (to exclude vma changes,
2663 * but allow concurrent faults), and pte mapped but not yet locked.
2664 * We return with mmap_sem still held, but pte unmapped and unlocked.
2665 */
2666static inline int handle_pte_fault(struct mm_struct *mm,
2667                struct vm_area_struct *vma, unsigned long address,
2668                pte_t *pte, pmd_t *pmd, int write_access)
2669{
2670        pte_t entry;
2671        spinlock_t *ptl;
2672
2673        entry = *pte;
2674        if (!pte_present(entry)) {
2675                if (pte_none(entry)) {
2676                        if (vma->vm_ops) {
2677                                if (likely(vma->vm_ops->fault))
2678                                        return do_linear_fault(mm, vma, address,
2679                                                pte, pmd, write_access, entry);
2680                        }
2681                        return do_anonymous_page(mm, vma, address,
2682                                                 pte, pmd, write_access);
2683                }
2684                if (pte_file(entry))
2685                        return do_nonlinear_fault(mm, vma, address,
2686                                        pte, pmd, write_access, entry);
2687                return do_swap_page(mm, vma, address,
2688                                        pte, pmd, write_access, entry);
2689        }
2690
2691        ptl = pte_lockptr(mm, pmd);
2692        spin_lock(ptl);
2693        if (unlikely(!pte_same(*pte, entry)))
2694                goto unlock;
2695        if (write_access) {
2696                if (!pte_write(entry))
2697                        return do_wp_page(mm, vma, address,
2698                                        pte, pmd, ptl, entry);
2699                entry = pte_mkdirty(entry);
2700        }
2701        entry = pte_mkyoung(entry);
2702        if (ptep_set_access_flags(vma, address, pte, entry, write_access)) {
2703                update_mmu_cache(vma, address, entry);
2704        } else {
2705                /*
2706                 * This is needed only for protection faults but the arch code
2707                 * is not yet telling us if this is a protection fault or not.
2708                 * This still avoids useless tlb flushes for .text page faults
2709                 * with threads.
2710                 */
2711                if (write_access)
2712                        flush_tlb_page(vma, address);
2713        }
2714unlock:
2715        pte_unmap_unlock(pte, ptl);
2716        return 0;
2717}
2718
2719/*
2720 * By the time we get here, we already hold the mm semaphore
2721 */
2722int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2723                unsigned long address, int write_access)
2724{
2725        pgd_t *pgd;
2726        pud_t *pud;
2727        pmd_t *pmd;
2728        pte_t *pte;
2729
2730        __set_current_state(TASK_RUNNING);
2731
2732        count_vm_event(PGFAULT);
2733
2734        if (unlikely(is_vm_hugetlb_page(vma)))
2735                return hugetlb_fault(mm, vma, address, write_access);
2736
2737        pgd = pgd_offset(mm, address);
2738        pud = pud_alloc(mm, pgd, address);
2739        if (!pud)
2740                return VM_FAULT_OOM;
2741        pmd = pmd_alloc(mm, pud, address);
2742        if (!pmd)
2743                return VM_FAULT_OOM;
2744        pte = pte_alloc_map(mm, pmd, address);
2745        if (!pte)
2746                return VM_FAULT_OOM;
2747
2748        return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
2749}
2750
2751#ifndef __PAGETABLE_PUD_FOLDED
2752/*
2753 * Allocate page upper directory.
2754 * We've already handled the fast-path in-line.
2755 */
2756int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
2757{
2758        pud_t *new = pud_alloc_one(mm, address);
2759        if (!new)
2760                return -ENOMEM;
2761
2762        smp_wmb(); /* See comment in __pte_alloc */
2763
2764        spin_lock(&mm->page_table_lock);
2765        if (pgd_present(*pgd))          /* Another has populated it */
2766                pud_free(mm, new);
2767        else
2768                pgd_populate(mm, pgd, new);
2769        spin_unlock(&mm->page_table_lock);
2770        return 0;
2771}
2772#endif /* __PAGETABLE_PUD_FOLDED */
2773
2774#ifndef __PAGETABLE_PMD_FOLDED
2775/*
2776 * Allocate page middle directory.
2777 * We've already handled the fast-path in-line.
2778 */
2779int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
2780{
2781        pmd_t *new = pmd_alloc_one(mm, address);
2782        if (!new)
2783                return -ENOMEM;
2784
2785        smp_wmb(); /* See comment in __pte_alloc */
2786
2787        spin_lock(&mm->page_table_lock);
2788#ifndef __ARCH_HAS_4LEVEL_HACK
2789        if (pud_present(*pud))          /* Another has populated it */
2790                pmd_free(mm, new);
2791        else
2792                pud_populate(mm, pud, new);
2793#else
2794        if (pgd_present(*pud))          /* Another has populated it */
2795                pmd_free(mm, new);
2796        else
2797                pgd_populate(mm, pud, new);
2798#endif /* __ARCH_HAS_4LEVEL_HACK */
2799        spin_unlock(&mm->page_table_lock);
2800        return 0;
2801}
2802#endif /* __PAGETABLE_PMD_FOLDED */
2803
2804int make_pages_present(unsigned long addr, unsigned long end)
2805{
2806        int ret, len, write;
2807        struct vm_area_struct * vma;
2808
2809        vma = find_vma(current->mm, addr);
2810        if (!vma)
2811                return -ENOMEM;
2812        write = (vma->vm_flags & VM_WRITE) != 0;
2813        BUG_ON(addr >= end);
2814        BUG_ON(end > vma->vm_end);
2815        len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
2816        ret = get_user_pages(current, current->mm, addr,
2817                        len, write, 0, NULL, NULL);
2818        if (ret < 0)
2819                return ret;
2820        return ret == len ? 0 : -EFAULT;
2821}
2822
2823#if !defined(__HAVE_ARCH_GATE_AREA)
2824
2825#if defined(AT_SYSINFO_EHDR)
2826static struct vm_area_struct gate_vma;
2827
2828static int __init gate_vma_init(void)
2829{
2830        gate_vma.vm_mm = NULL;
2831        gate_vma.vm_start = FIXADDR_USER_START;
2832        gate_vma.vm_end = FIXADDR_USER_END;
2833        gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
2834        gate_vma.vm_page_prot = __P101;
2835        /*
2836         * Make sure the vDSO gets into every core dump.
2837         * Dumping its contents makes post-mortem fully interpretable later
2838         * without matching up the same kernel and hardware config to see
2839         * what PC values meant.
2840         */
2841        gate_vma.vm_flags |= VM_ALWAYSDUMP;
2842        return 0;
2843}
2844__initcall(gate_vma_init);
2845#endif
2846
2847struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
2848{
2849#ifdef AT_SYSINFO_EHDR
2850        return &gate_vma;
2851#else
2852        return NULL;
2853#endif
2854}
2855
2856int in_gate_area_no_task(unsigned long addr)
2857{
2858#ifdef AT_SYSINFO_EHDR
2859        if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
2860                return 1;
2861#endif
2862        return 0;
2863}
2864
2865#endif  /* __HAVE_ARCH_GATE_AREA */
2866
2867#ifdef CONFIG_HAVE_IOREMAP_PROT
2868static resource_size_t follow_phys(struct vm_area_struct *vma,
2869                        unsigned long address, unsigned int flags,
2870                        unsigned long *prot)
2871{
2872        pgd_t *pgd;
2873        pud_t *pud;
2874        pmd_t *pmd;
2875        pte_t *ptep, pte;
2876        spinlock_t *ptl;
2877        resource_size_t phys_addr = 0;
2878        struct mm_struct *mm = vma->vm_mm;
2879
2880        VM_BUG_ON(!(vma->vm_flags & (VM_IO | VM_PFNMAP)));
2881
2882        pgd = pgd_offset(mm, address);
2883        if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
2884                goto no_page_table;
2885
2886        pud = pud_offset(pgd, address);
2887        if (pud_none(*pud) || unlikely(pud_bad(*pud)))
2888                goto no_page_table;
2889
2890        pmd = pmd_offset(pud, address);
2891        if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
2892                goto no_page_table;
2893
2894        /* We cannot handle huge page PFN maps. Luckily they don't exist. */
2895        if (pmd_huge(*pmd))
2896                goto no_page_table;
2897
2898        ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
2899        if (!ptep)
2900                goto out;
2901
2902        pte = *ptep;
2903        if (!pte_present(pte))
2904                goto unlock;
2905        if ((flags & FOLL_WRITE) && !pte_write(pte))
2906                goto unlock;
2907        phys_addr = pte_pfn(pte);
2908        phys_addr <<= PAGE_SHIFT; /* Shift here to avoid overflow on PAE */
2909
2910        *prot = pgprot_val(pte_pgprot(pte));
2911
2912unlock:
2913        pte_unmap_unlock(ptep, ptl);
2914out:
2915        return phys_addr;
2916no_page_table:
2917        return 0;
2918}
2919
2920int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
2921                        void *buf, int len, int write)
2922{
2923        resource_size_t phys_addr;
2924        unsigned long prot = 0;
2925        void *maddr;
2926        int offset = addr & (PAGE_SIZE-1);
2927
2928        if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
2929                return -EINVAL;
2930
2931        phys_addr = follow_phys(vma, addr, write, &prot);
2932
2933        if (!phys_addr)
2934                return -EINVAL;
2935
2936        maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
2937        if (write)
2938                memcpy_toio(maddr + offset, buf, len);
2939        else
2940                memcpy_fromio(buf, maddr + offset, len);
2941        iounmap(maddr);
2942
2943        return len;
2944}
2945#endif
2946
2947/*
2948 * Access another process' address space.
2949 * Source/target buffer must be kernel space,
2950 * Do not walk the page table directly, use get_user_pages
2951 */
2952int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
2953{
2954        struct mm_struct *mm;
2955        struct vm_area_struct *vma;
2956        void *old_buf = buf;
2957
2958        mm = get_task_mm(tsk);
2959        if (!mm)
2960                return 0;
2961
2962        down_read(&mm->mmap_sem);
2963        /* ignore errors, just check how much was successfully transferred */
2964        while (len) {
2965                int bytes, ret, offset;
2966                void *maddr;
2967                struct page *page = NULL;
2968
2969                ret = get_user_pages(tsk, mm, addr, 1,
2970                                write, 1, &page, &vma);
2971                if (ret <= 0) {
2972                        /*
2973                         * Check if this is a VM_IO | VM_PFNMAP VMA, which
2974                         * we can access using slightly different code.
2975                         */
2976#ifdef CONFIG_HAVE_IOREMAP_PROT
2977                        vma = find_vma(mm, addr);
2978                        if (!vma)
2979                                break;
2980                        if (vma->vm_ops && vma->vm_ops->access)
2981                                ret = vma->vm_ops->access(vma, addr, buf,
2982                                                          len, write);
2983                        if (ret <= 0)
2984#endif
2985                                break;
2986                        bytes = ret;
2987                } else {
2988                        bytes = len;
2989                        offset = addr & (PAGE_SIZE-1);
2990                        if (bytes > PAGE_SIZE-offset)
2991                                bytes = PAGE_SIZE-offset;
2992
2993                        maddr = kmap(page);
2994                        if (write) {
2995                                copy_to_user_page(vma, page, addr,
2996                                                  maddr + offset, buf, bytes);
2997                                set_page_dirty_lock(page);
2998                        } else {
2999                                copy_from_user_page(vma, page, addr,
3000                                                    buf, maddr + offset, bytes);
3001                        }
3002                        kunmap(page);
3003                        page_cache_release(page);
3004                }
3005                len -= bytes;
3006                buf += bytes;
3007                addr += bytes;
3008        }
3009        up_read(&mm->mmap_sem);
3010        mmput(mm);
3011
3012        return buf - old_buf;
3013}
3014
3015/*
3016 * Print the name of a VMA.
3017 */
3018void print_vma_addr(char *prefix, unsigned long ip)
3019{
3020        struct mm_struct *mm = current->mm;
3021        struct vm_area_struct *vma;
3022
3023        /*
3024         * Do not print if we are in atomic
3025         * contexts (in exception stacks, etc.):
3026         */
3027        if (preempt_count())
3028                return;
3029
3030        down_read(&mm->mmap_sem);
3031        vma = find_vma(mm, ip);
3032        if (vma && vma->vm_file) {
3033                struct file *f = vma->vm_file;
3034                char *buf = (char *)__get_free_page(GFP_KERNEL);
3035                if (buf) {
3036                        char *p, *s;
3037
3038                        p = d_path(&f->f_path, buf, PAGE_SIZE);
3039                        if (IS_ERR(p))
3040                                p = "?";
3041                        s = strrchr(p, '/');
3042                        if (s)
3043                                p = s+1;
3044                        printk("%s%s[%lx+%lx]", prefix, p,
3045                                        vma->vm_start,
3046                                        vma->vm_end - vma->vm_start);
3047                        free_page((unsigned long)buf);
3048                }
3049        }
3050        up_read(&current->mm->mmap_sem);
3051}
3052
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