1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1994-1999 Linus Torvalds
9 * The msync() system call.
13 #include <linux/mman.h>
14 #include <linux/file.h>
15 #include <linux/syscalls.h>
16 #include <linux/sched.h>
19 * MS_SYNC syncs the entire file - including mappings.
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.
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
32 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
35 struct mm_struct *mm = current->mm;
36 struct vm_area_struct *vma;
37 int unmapped_error = 0;
40 if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
42 if (offset_in_page(start))
44 if ((flags & MS_ASYNC) && (flags & MS_SYNC))
47 len = (len + ~PAGE_MASK) & PAGE_MASK;
55 * If the interval [start,end) covers some unmapped address ranges,
56 * just ignore them, but return -ENOMEM at the end.
58 down_read(&mm->mmap_sem);
59 vma = find_vma(mm, start);
64 /* Still start < end. */
68 /* Here start < vma->vm_end. */
69 if (start < vma->vm_start) {
70 start = vma->vm_start;
73 unmapped_error = -ENOMEM;
75 /* Here vma->vm_start <= start < vma->vm_end. */
76 if ((flags & MS_INVALIDATE) &&
77 (vma->vm_flags & VM_LOCKED)) {
82 fstart = (start - vma->vm_start) +
83 ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
84 fend = fstart + (min(end, vma->vm_end) - start) - 1;
86 if ((flags & MS_SYNC) && file &&
87 (vma->vm_flags & VM_SHARED)) {
89 up_read(&mm->mmap_sem);
90 error = vfs_fsync_range(file, fstart, fend, 1);
92 if (error || start >= end)
94 down_read(&mm->mmap_sem);
95 vma = find_vma(mm, start);
105 up_read(&mm->mmap_sem);
107 return error ? : unmapped_error;