#include <sys/param.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <sys/mount.h>
#include <sys/uio.h>

#include <assert.h>
#include <err.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>

#define	fsmount	"/mnt"
#define	fstype	"fdescfs"
#define	fsmod	"fdescfs"

static void
kmod_load(void)
{
	int error;

	error = kldload(fsmod);
	assert(error != 0);
}

static void
kmod_unload(void)
{
	int id;

	id = kldfind(fsmod);
	if (id != -1)
		(void)kldunload(id);
}

static void *
thread_kmod(void *data __unused)
{

	for (;;) {
		kmod_load();
		kmod_unload();
	}

	return (NULL);
}

static void
fs_mount(const char *mntpoint)
{
	struct iovec iov[6];

	iov[0].iov_base = "fstype";
	iov[0].iov_len = sizeof("fstype");

	iov[1].iov_base = fstype;
	iov[1].iov_len = sizeof(fstype);

	iov[2].iov_base = "fspath";
	iov[2].iov_len = sizeof("fspath");

	iov[3].iov_base = mntpoint;
	iov[3].iov_len = strlen(mntpoint) + 1;

	iov[4].iov_base = "from";
	iov[4].iov_len = sizeof("from");

	iov[5].iov_base = fstype;
	iov[5].iov_len = sizeof(fstype);

	nmount(iov, nitems(iov), 0);
}

static void *
thread_mount(void *data __unused)
{

	for (;;) {
		fs_mount(fsmount);
		unmount(fsmount, 0);
	}

	return (NULL);
}

int
main(int argc, char *argv[])
{
	pthread_t hdl[2];
	int error;

	unmount(fsmount, 0);
	kmod_unload();

	error = pthread_create(&hdl[0], NULL, thread_kmod, NULL);
	assert(error == 0);
	error = pthread_create(&hdl[1], NULL, thread_mount, NULL);
	assert(error == 0);

	pthread_join(hdl[0], NULL);
	pthread_join(hdl[1], NULL);
}