msync.c revision e8edc6e03a5c8562dc70a6d969f732bdb355a7e7 
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 */
31asmlinkage long sys_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
62		/* Still start < end. */
63		error = -ENOMEM;
64		if (!vma)
65			goto out_unlock;
66		/* Here start < vma->vm_end. */
67		if (start < vma->vm_start) {
68			start = vma->vm_start;
69			if (start >= end)
70				goto out_unlock;
71			unmapped_error = -ENOMEM;
72		}
73		/* Here vma->vm_start <= start < vma->vm_end. */
74		if ((flags & MS_INVALIDATE) &&
75				(vma->vm_flags & VM_LOCKED)) {
76			error = -EBUSY;
77			goto out_unlock;
78		}
79		file = vma->vm_file;
80		start = vma->vm_end;
81		if ((flags & MS_SYNC) && file &&
82				(vma->vm_flags & VM_SHARED)) {
83			get_file(file);
84			up_read(&mm->mmap_sem);
85			error = do_fsync(file, 0);
86			fput(file);
87			if (error || start >= end)
88				goto out;
89			down_read(&mm->mmap_sem);
90			vma = find_vma(mm, start);
91		} else {
92			if (start >= end) {
93				error = 0;
94				goto out_unlock;
95			}
96			vma = vma->vm_next;
97		}
98	}
99out_unlock:
100	up_read(&mm->mmap_sem);
101out:
102	return error ? : unmapped_error;
103}
104