xref: /openbmc/linux/mm/msync.c (revision 19c233b7)
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 #include <linux/sched.h>
16 
17 /*
18  * MS_SYNC syncs the entire file - including mappings.
19  *
20  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
21  * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
22  * Now it doesn't do anything, since dirty pages are properly tracked.
23  *
24  * The application may now run fsync() to
25  * write out the dirty pages and wait on the writeout and check the result.
26  * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
27  * async writeout immediately.
28  * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
29  * applications.
30  */
31 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
32 {
33 	unsigned long end;
34 	struct mm_struct *mm = current->mm;
35 	struct vm_area_struct *vma;
36 	int unmapped_error = 0;
37 	int error = -EINVAL;
38 
39 	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
40 		goto out;
41 	if (start & ~PAGE_MASK)
42 		goto out;
43 	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
44 		goto out;
45 	error = -ENOMEM;
46 	len = (len + ~PAGE_MASK) & PAGE_MASK;
47 	end = start + len;
48 	if (end < start)
49 		goto out;
50 	error = 0;
51 	if (end == start)
52 		goto out;
53 	/*
54 	 * If the interval [start,end) covers some unmapped address ranges,
55 	 * just ignore them, but return -ENOMEM at the end.
56 	 */
57 	down_read(&mm->mmap_sem);
58 	vma = find_vma(mm, start);
59 	for (;;) {
60 		struct file *file;
61 		loff_t fstart, fend;
62 
63 		/* Still start < end. */
64 		error = -ENOMEM;
65 		if (!vma)
66 			goto out_unlock;
67 		/* Here start < vma->vm_end. */
68 		if (start < vma->vm_start) {
69 			start = vma->vm_start;
70 			if (start >= end)
71 				goto out_unlock;
72 			unmapped_error = -ENOMEM;
73 		}
74 		/* Here vma->vm_start <= start < vma->vm_end. */
75 		if ((flags & MS_INVALIDATE) &&
76 				(vma->vm_flags & VM_LOCKED)) {
77 			error = -EBUSY;
78 			goto out_unlock;
79 		}
80 		file = vma->vm_file;
81 		fstart = (start - vma->vm_start) +
82 			 ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
83 		fend = fstart + (min(end, vma->vm_end) - start) - 1;
84 		start = vma->vm_end;
85 		if ((flags & MS_SYNC) && file &&
86 				(vma->vm_flags & VM_SHARED)) {
87 			get_file(file);
88 			up_read(&mm->mmap_sem);
89 			error = vfs_fsync_range(file, fstart, fend, 1);
90 			fput(file);
91 			if (error || start >= end)
92 				goto out;
93 			down_read(&mm->mmap_sem);
94 			vma = find_vma(mm, start);
95 		} else {
96 			if (start >= end) {
97 				error = 0;
98 				goto out_unlock;
99 			}
100 			vma = vma->vm_next;
101 		}
102 	}
103 out_unlock:
104 	up_read(&mm->mmap_sem);
105 out:
106 	return error ? : unmapped_error;
107 }
108