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