linux/mm/msync.c
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   1/*
   2 *      linux/mm/msync.c
   3 *
   4 * Copyright (C) 1994-1999  Linus Torvalds
   5 */
   6
   7/*
   8 * The msync() system call.
   9 */
  10#include <linux/fs.h>
  11#include <linux/mm.h>
  12#include <linux/mman.h>
  13#include <linux/file.h>
  14#include <linux/syscalls.h>
  15#include <linux/sched.h>
  16
  17/*
  18 * MS_SYNC syncs the entire file - including mappings.
  19 *
  20 * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
  21 * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
  22 * Now it doesn't do anything, since dirty pages are properly tracked.
  23 *
  24 * The application may now run fsync() to
  25 * write out the dirty pages and wait on the writeout and check the result.
  26 * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
  27 * async writeout immediately.
  28 * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
  29 * applications.
  30 */
  31SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
  32{
  33        unsigned long end;
  34        struct mm_struct *mm = current->mm;
  35        struct vm_area_struct *vma;
  36        int unmapped_error = 0;
  37        int error = -EINVAL;
  38
  39        if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
  40                goto out;
  41        if (start & ~PAGE_MASK)
  42                goto out;
  43        if ((flags & MS_ASYNC) && (flags & MS_SYNC))
  44                goto out;
  45        error = -ENOMEM;
  46        len = (len + ~PAGE_MASK) & PAGE_MASK;
  47        end = start + len;
  48        if (end < start)
  49                goto out;
  50        error = 0;
  51        if (end == start)
  52                goto out;
  53        /*
  54         * If the interval [start,end) covers some unmapped address ranges,
  55         * just ignore them, but return -ENOMEM at the end.
  56         */
  57        down_read(&mm->mmap_sem);
  58        vma = find_vma(mm, start);
  59        for (;;) {
  60                struct file *file;
  61
  62                /* Still start < end. */
  63                error = -ENOMEM;
  64                if (!vma)
  65                        goto out_unlock;
  66                /* Here start < vma->vm_end. */
  67                if (start < vma->vm_start) {
  68                        start = vma->vm_start;
  69                        if (start >= end)
  70                                goto out_unlock;
  71                        unmapped_error = -ENOMEM;
  72                }
  73                /* Here vma->vm_start <= start < vma->vm_end. */
  74                if ((flags & MS_INVALIDATE) &&
  75                                (vma->vm_flags & VM_LOCKED)) {
  76                        error = -EBUSY;
  77                        goto out_unlock;
  78                }
  79                file = vma->vm_file;
  80                start = vma->vm_end;
  81                if ((flags & MS_SYNC) && file &&
  82                                (vma->vm_flags & VM_SHARED)) {
  83                        get_file(file);
  84                        up_read(&mm->mmap_sem);
  85                        error = vfs_fsync(file, 0);
  86                        fput(file);
  87                        if (error || start >= end)
  88                                goto out;
  89                        down_read(&mm->mmap_sem);
  90                        vma = find_vma(mm, start);
  91                } else {
  92                        if (start >= end) {
  93                                error = 0;
  94                                goto out_unlock;
  95                        }
  96                        vma = vma->vm_next;
  97                }
  98        }
  99out_unlock:
 100        up_read(&mm->mmap_sem);
 101out:
 102        return error ? : unmapped_error;
 103}
 104
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