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, addr: 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(f: file);
95 mmap_read_unlock(mm);
96 error = vfs_fsync_range(file, start: fstart, end: fend, datasync: 1);
97 fput(file);
98 if (error || start >= end)
99 goto out;
100 mmap_read_lock(mm);
101 vma = find_vma(mm, addr: start);
102 } else {
103 if (start >= end) {
104 error = 0;
105 goto out_unlock;
106 }
107 vma = find_vma(mm, addr: vma->vm_end);
108 }
109 }
110out_unlock:
111 mmap_read_unlock(mm);
112out:
113 return error ? : unmapped_error;
114}
115