how to access file in kernel space

static void write_file(char *filename, unsigned char *data, unsigned int nSize)

{

struct file *file;

loff_t pos = 0;

int fd;

dmac_inv_range(data, data + nSize);

mm_segment_t old_fs = get_fs();

set_fs(KERNEL_DS);

fd = sys_open(filename, O_WRONLY|O_CREAT, 0644);

if (fd >= 0) {

sys_write(fd, data, nSize);

file = fget(fd);

if (file) {

vfs_write(file, data, nSize, &pos);

fput(file);

}

sys_close(fd);

}

else

{

mfc_err("........Open fail : %d \n", fd);

}

set_fs(old_fs);

dmac_clean_range(data, data + nSize);

}