Root/mm/msync.c

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 */
31SYSCALL_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
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 = vfs_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

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