cdp_c has incomplete type error

[Jun Furukawa]

When　I compiled the following C language code which hooks vn_write function
on FreeBSD8.2,
I get "error: field 'cdp_c' has incomplete type" error.
Here we list the C source code, Makefile and the compiler messages.
Can anyone help me please?
************************vn_hook.c***********************************
#include <sys/param.h> /* module */
#include <sys/module.h> /* module */
#include <sys/kernel.h> /* module */
#include <sys/types.h> /* size_t, copyin, copyout, malloc */
#include <sys/systm.h> /* copyin, copyout */
#include <sys/proc.h> /* struct thread */
#include <sys/file.h> /* vnops */
#include <fs/msdosfs/msdosfs_vnops.c> /* msdosfs_vnodeops */
#include <sys/malloc.h> /* malloc */
#include <fs/devfs/devfs_int.h> /* cdpd_data */
typedef int (*vnw_t)(struct file*,
struct uio*,
struct ucred*,
int flags,
struct thread*);

int
vn_write_hook(struct file *fp,
struct uio *uio,
struct ucred *active_cred,
int flags,
struct thread *td);
int
caesar_encrypt (char *str, int len, int key);

vnw_t old_vn_write;
/* caesar encription */
int
caesar_encrypt (char *str, int len, int key)
{
int i;
for (i = 0; i < len ; i++) {
if (str[i] != '\0') {
str[i] += key;
}
}
return 0;
}

/* vn_write hook */
int
vn_write_hook(struct file *fp,
struct uio *uio,
struct ucred *active_cred,
int flags,
struct thread *td)
{

/* The definition of struct file */
/* from /usr/include/sys/file.h */
//struct file {
// ...
// struct vnode *f_vnode; /* NULL or applicable vnode */
// ... for f_offset */
//
// struct cdev_privdata *f_cdevpriv; /* (d) Private data
// for the cdev. */
//};

/* The definition of vnode */
/* from /usr/include/sys/vnode.h */
//struct vnode {
// ...
// const char *v_tag; /* u type of
// underlying data */
// ...
//};

/* The definition of struct iovec */
/* from /usr/include/sys/_iovec.h */
//struct iovec {
// void *iov_base; /* Base address. */
// size_t iov_len; /* Length. */
//};

/* The definition of struct uio */
/* from /usr/include/sys/uio.h */
//struct uio {
//struct iovec *uio_iov; /* scatter/gather list */
//...
//};

/* struct cdev_privdata */
/* from /usr/include/fs/devfs/devfs_int.h */
//struct cdev_privdata {
// struct file *cdpd_fp;
// void *cdpd_data;
// void (*cdpd_dtr)(void *);
// LIST_ENTRY(cdev_privdata) cdpd_list;
//};

/* Is the destination msdosfs ? */
if(!strncmp("msdosfs",fp->f_vnode->v_tag,7)) {
int error; int iov_len;
char *mybuf;
iov_len = uio->uio_iov->iov_len;
mybuf = (char *)malloc(iov_len,M_TEMP,M_NOWAIT|M_ZERO);

/* copy data from user land to kernel land */
error = copyin(uio->uio_iov->iov_base,
mybuf,
iov_len);
if (error != 0) {
uprintf("Cannot write data to kernel space\n");
}
/* debug */
// uprintf("cdev_priv:%p",
// (char *)fp->f_cdevpriv->cdpd_data);

/* encrypt by caesar algorithm */
caesar_encrypt(mybuf, iov_len, 3);

/* copy data from kernel land to user land */
error = copyout(mybuf,
uio->uio_iov->iov_base,
iov_len);

if (error != 0) {
uprintf("Cannot write data to user space\n");
}
free(mybuf,M_TEMP);
}
return (old_vn_write(fp, uio, active_cred, flags, td));
}

/* The function called at load/unload */
static int
load(struct module *module, int cmd, void *arg)
{
int error = 0;

/* the initial value of vnops */
/* from /usr/src/sys/kern/vfs_vnops.c */
//struct fileops vnops = {
// .fo_read = vn_read,
// .fo_write = vn_write,
// .fo_truncate = vn_truncate,
// .fo_ioctl = vn_ioctl,
// .fo_poll = vn_poll,
// .fo_kqfilter = vn_kqfilter,
// .fo_stat = vn_statfile,
// .fo_close = vn_closefile,
// .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
//};
switch (cmd) {
case MOD_LOAD:
uprintf("Module has loaded\n");
/* Replace vn_write with vn_write_hook. */
old_vn_write = (vnw_t)(vnops.fo_write);
vnops.fo_write = vn_write_hook;

break;

case MOD_UNLOAD:
uprintf("Module has unloaded\n");

/* Change everyhting back to normal. */
vnops.fo_write = old_vn_write;
break;

default:
error = EOPNOTSUPP;
break;
}

return (error);
}

static moduledata_t vn_write_hook_mod = {
"vn_write_hook", /* module name */
load, /* event handler */
NULL /* EXTRA DATA */
};

DECLARE_MODULE(vn_write_hook, vn_write_hook_mod,
SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
************************vn_hook.c***********************************

************************Makefile************************************
KMOD = vn_hook # Name of KLD to build.
SRCS = vnode_if.h vn_hook.c # List of source files.
.include <bsd.kmod.mk
************************Makefile***********************************

************************Compiler Message****************************
Warning: Object directory not changed from original /usr/home/jun/vn_hook
cc -O2 -pipe -fno-strict-aliasing -Werror -D_KERNEL -DKLD_MODULE
-nostdinc -I. -I@ -I@/contrib/altq -finline-limit=8000 --param
inline-unit-growth=100 --param large-function-growth=1000 -fno-common
-mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow
-mno-sse -mno-sse2 -mno-sse3 -ffreestanding -fstack-protector
-std=iso9899:1999 -fstack-protector -Wall -Wredundant-decls
-Wnested-externs -Wstrict-prototypes -Wmissing-prototypes
-Wpointer-arith -Winline -Wcast-qual -Wundef -Wno-pointer-sign
-fformat-extensions -c vn_hook.c
*** Error code 1

Stop in /usr/home/jun/vn_hook.
Warning: Object directory not changed from original /usr/home/jun/vn_hook
cc -O2 -pipe -fno-strict-aliasing -Werror -D_KERNEL -DKLD_MODULE
-nostdinc -I. -I@ -I@/contrib/altq -finline-limit=8000 --param
inline-unit-growth=100 --param large-function-growth=1000 -fno-common
-mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow
-mno-sse -mno-sse2 -mno-sse3 -ffreestanding -fstack-protector
-std=iso9899:1999 -fstack-protector -Wall -Wredundant-decls
-Wnested-externs -Wstrict-prototypes -Wmissing-prototypes
-Wpointer-arith -Winline -Wcast-qual -Wundef -Wno-pointer-sign
-fformat-extensions -c vn_hook.c
In file included from vn_hook.c:10:
@/fs/devfs/devfs_int.h:50: error: field 'cdp_c' has incomplete type
*** Error code 1

Stop in /usr/home/jun/vn_hook.
************************Compiler Message*****************************

Jun Furukawa