xref: /openbmc/linux/mm/msync.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  *	linux/mm/msync.c
3  *
4  * Copyright (C) 1994-1999  Linus Torvalds
5  */
6 
7 /*
8  * The msync() system call.
9  */
10 #include <linux/fs.h>
11 #include <linux/mm.h>
12 #include <linux/mman.h>
13 #include <linux/file.h>
14 #include <linux/syscalls.h>
15 
16 /*
17  * MS_SYNC syncs the entire file - including mappings.
18  *
19  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
20  * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
21  * Now it doesn't do anything, since dirty pages are properly tracked.
22  *
23  * The application may now run fsync() to
24  * write out the dirty pages and wait on the writeout and check the result.
25  * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
26  * async writeout immediately.
27  * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
28  * applications.
29  */
30 asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
31 {
32 	unsigned long end;
33 	struct mm_struct *mm = current->mm;
34 	struct vm_area_struct *vma;
35 	int unmapped_error = 0;
36 	int error = -EINVAL;
37 
38 	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
39 		goto out;
40 	if (start & ~PAGE_MASK)
41 		goto out;
42 	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
43 		goto out;
44 	error = -ENOMEM;
45 	len = (len + ~PAGE_MASK) & PAGE_MASK;
46 	end = start + len;
47 	if (end < start)
48 		goto out;
49 	error = 0;
50 	if (end == start)
51 		goto out;
52 	/*
53 	 * If the interval [start,end) covers some unmapped address ranges,
54 	 * just ignore them, but return -ENOMEM at the end.
55 	 */
56 	down_read(&mm->mmap_sem);
57 	vma = find_vma(mm, start);
58 	for (;;) {
59 		struct file *file;
60 
61 		/* Still start < end. */
62 		error = -ENOMEM;
63 		if (!vma)
64 			goto out_unlock;
65 		/* Here start < vma->vm_end. */
66 		if (start < vma->vm_start) {
67 			start = vma->vm_start;
68 			if (start >= end)
69 				goto out_unlock;
70 			unmapped_error = -ENOMEM;
71 		}
72 		/* Here vma->vm_start <= start < vma->vm_end. */
73 		if ((flags & MS_INVALIDATE) &&
74 				(vma->vm_flags & VM_LOCKED)) {
75 			error = -EBUSY;
76 			goto out_unlock;
77 		}
78 		file = vma->vm_file;
79 		start = vma->vm_end;
80 		if ((flags & MS_SYNC) && file &&
81 				(vma->vm_flags & VM_SHARED)) {
82 			get_file(file);
83 			up_read(&mm->mmap_sem);
84 			error = do_fsync(file, 0);
85 			fput(file);
86 			if (error || start >= end)
87 				goto out;
88 			down_read(&mm->mmap_sem);
89 			vma = find_vma(mm, start);
90 		} else {
91 			if (start >= end) {
92 				error = 0;
93 				goto out_unlock;
94 			}
95 			vma = vma->vm_next;
96 		}
97 	}
98 out_unlock:
99 	up_read(&mm->mmap_sem);
100 out:
101 	return error ? : unmapped_error;
102 }
103