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. 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 | } |
110 | out_unlock: |
111 | mmap_read_unlock(mm); |
112 | out: |
113 | return error ? : unmapped_error; |
114 | } |
115 | |