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 */
32SYSCALL_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	start = untagged_addr(start);
41
42	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
43		goto out;
44	if (offset_in_page(start))
45		goto out;
46	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
47		goto out;
48	error = -ENOMEM;
49	len = (len + ~PAGE_MASK) & PAGE_MASK;
50	end = start + len;
51	if (end < start)
52		goto out;
53	error = 0;
54	if (end == start)
55		goto out;
56	/*
57	 * If the interval [start,end) covers some unmapped address ranges,
58	 * just ignore them, but return -ENOMEM at the end. Besides, if the
59	 * flag is MS_ASYNC (w/o MS_INVALIDATE) the result would be -ENOMEM
60	 * anyway and there is nothing left to do, so return immediately.
61	 */
62	mmap_read_lock(mm);
63	vma = find_vma(mm, start);
64	for (;;) {
65		struct file *file;
66		loff_t fstart, fend;
67
68		/* Still start < end. */
69		error = -ENOMEM;
70		if (!vma)
71			goto out_unlock;
72		/* Here start < vma->vm_end. */
73		if (start < vma->vm_start) {
74			if (flags == MS_ASYNC)
75				goto out_unlock;
76			start = vma->vm_start;
77			if (start >= end)
78				goto out_unlock;
79			unmapped_error = -ENOMEM;
80		}
81		/* Here vma->vm_start <= start < vma->vm_end. */
82		if ((flags & MS_INVALIDATE) &&
83				(vma->vm_flags & VM_LOCKED)) {
84			error = -EBUSY;
85			goto out_unlock;
86		}
87		file = vma->vm_file;
88		fstart = (start - vma->vm_start) +
89			 ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
90		fend = fstart + (min(end, vma->vm_end) - start) - 1;
91		start = vma->vm_end;
92		if ((flags & MS_SYNC) && file &&
93				(vma->vm_flags & VM_SHARED)) {
94			get_file(file);
95			mmap_read_unlock(mm);
96			error = vfs_fsync_range(file, fstart, fend, 1);
97			fput(file);
98			if (error || start >= end)
99				goto out;
100			mmap_read_lock(mm);
101			vma = find_vma(mm, start);
102		} else {
103			if (start >= end) {
104				error = 0;
105				goto out_unlock;
106			}
107			vma = vma->vm_next;
108		}
109	}
110out_unlock:
111	mmap_read_unlock(mm);
112out:
113	return error ? : unmapped_error;
114}
115