mm/msync.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      linux/mm/msync.c
   4  *
   5  * Copyright (C) 1994-1999  Linus Torvalds
   6  */
   7
   8 /*
   9  * The msync() system call.
  10  */
  11 #include <linux/fs.h>
  12 #include <linux/mm.h>
  13 #include <linux/mman.h>
  14 #include <linux/file.h>
  15 #include <linux/syscalls.h>
  16 #include <linux/sched.h>
  17
  18 /*
  19  * MS_SYNC syncs the entire file - including mappings.
  20  *
  21  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
  22  * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
  23  * Now it doesn't do anything, since dirty pages are properly tracked.
  24  *
  25  * The application may now run fsync() to
  26  * write out the dirty pages and wait on the writeout and check the result.
  27  * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
  28  * async writeout immediately.
  29  * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
  30  * applications.
  31  */
  32 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
  33 {
  34         unsigned long end;
  35         struct mm_struct *mm = current->mm;
  36         struct vm_area_struct *vma;
  37         int unmapped_error = 0;
  38         int error = -EINVAL;
  39
  40         if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
  41                 goto out;
  42         if (offset_in_page(start))
  43                 goto out;
  44         if ((flags & MS_ASYNC) && (flags & MS_SYNC))
  45                 goto out;
  46         error = -ENOMEM;
  47         len = (len + ~PAGE_MASK) & PAGE_MASK;
  48         end = start + len;
  49         if (end < start)
  50                 goto out;
  51         error = 0;
  52         if (end == start)
  53                 goto out;
  54         /*
  55          * If the interval [start,end) covers some unmapped address ranges,
  56          * just ignore them, but return -ENOMEM at the end.
  57          */
  58         down_read(&mm->mmap_sem);
  59         vma = find_vma(mm, start);
  60         for (;;) {
  61                 struct file *file;
  62                 loff_t fstart, fend;
  63
  64                 /* Still start < end. */
  65                 error = -ENOMEM;
  66                 if (!vma)
  67                         goto out_unlock;
  68                 /* Here start < vma->vm_end. */
  69                 if (start < vma->vm_start) {
  70                         start = vma->vm_start;
  71                         if (start >= end)
  72                                 goto out_unlock;
  73                         unmapped_error = -ENOMEM;
  74                 }
  75                 /* Here vma->vm_start <= start < vma->vm_end. */
  76                 if ((flags & MS_INVALIDATE) &&
  77                                 (vma->vm_flags & VM_LOCKED)) {
  78                         error = -EBUSY;
  79                         goto out_unlock;
  80                 }
  81                 file = vma->vm_file;
  82                 fstart = (start - vma->vm_start) +
  83                          ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
  84                 fend = fstart + (min(end, vma->vm_end) - start) - 1;
  85                 start = vma->vm_end;
  86                 if ((flags & MS_SYNC) && file &&
  87                                 (vma->vm_flags & VM_SHARED)) {
  88                         get_file(file);
  89                         up_read(&mm->mmap_sem);
  90                         error = vfs_fsync_range(file, fstart, fend, 1);
  91                         fput(file);
  92                         if (error || start >= end)
  93                                 goto out;
  94                         down_read(&mm->mmap_sem);
  95                         vma = find_vma(mm, start);
  96                 } else {
  97                         if (start >= end) {
  98                                 error = 0;
  99                                 goto out_unlock;
 100                         }
 101                         vma = vma->vm_next;
 102                 }
 103         }
 104 out_unlock:
 105         up_read(&mm->mmap_sem);
 106 out:
 107         return error ? : unmapped_error;
 108 }