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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  */
  31 asmlinkage long sys_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 = do_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         }
  99 out_unlock:
 100         up_read(&mm->mmap_sem);
 101 out:
 102         return error ? : unmapped_error;
 103 }