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 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.
59 */
60 down_read(&mm->mmap_sem);
61 vma = find_vma(mm, start);
62 for (;;) {
63 struct file *file;
64 loff_t fstart, fend;
65
66 /* Still start < end. */
67 error = -ENOMEM;
68 if (!vma)
69 goto out_unlock;
70 /* Here start < vma->vm_end. */
71 if (start < vma->vm_start) {
72 start = vma->vm_start;
73 if (start >= end)
74 goto out_unlock;
75 unmapped_error = -ENOMEM;
76 }
77 /* Here vma->vm_start <= start < vma->vm_end. */
78 if ((flags & MS_INVALIDATE) &&
79 (vma->vm_flags & VM_LOCKED)) {
80 error = -EBUSY;
81 goto out_unlock;
82 }
83 file = vma->vm_file;
84 fstart = (start - vma->vm_start) +
85 ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
86 fend = fstart + (min(end, vma->vm_end) - start) - 1;
87 start = vma->vm_end;
88 if ((flags & MS_SYNC) && file &&
89 (vma->vm_flags & VM_SHARED)) {
90 get_file(file);
91 up_read(&mm->mmap_sem);
92 error = vfs_fsync_range(file, fstart, fend, 1);
93 fput(file);
94 if (error || start >= end)
95 goto out;
96 down_read(&mm->mmap_sem);
97 vma = find_vma(mm, start);
98 } else {
99 if (start >= end) {
100 error = 0;
101 goto out_unlock;
102 }
103 vma = vma->vm_next;
104 }
105 }
106 out_unlock:
107 up_read(&mm->mmap_sem);
108 out:
109 return error ? : unmapped_error;
110 }