diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index f830b1b..d52ad24 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -109,14 +109,29 @@
 	unsigned char	addr[FLT_EXACT_COUNT][ETH_ALEN];
 };
 
+/* A tun_file connects an open character device to a tuntap netdevice. It
+ * also contains all socket related strctures (except sock_fprog and tap_filter)
+ * to serve as one transmit queue for tuntap device. The sock_fprog and
+ * tap_filter were kept in tun_struct since they were used for filtering for the
+ * netdevice not for a specific queue (at least I didn't see the reqirement for
+ * this).
+ */
 struct tun_file {
+	struct sock sk;
+	struct socket socket;
+	struct socket_wq wq;
 	atomic_t count;
 	struct tun_struct *tun;
 	struct net *net;
+	struct fasync_struct *fasync;
+	/* only used for fasnyc */
+	unsigned int flags;
 };
 
-struct tun_sock;
-
+/* Since the socket were moved to tun_file, to preserve the behavior of persist
+ * device, socket fileter, sndbuf and vnet header size were restore when the
+ * file were attached to a persist device.
+ */
 struct tun_struct {
 	struct tun_file		*tfile;
 	unsigned int 		flags;
@@ -127,29 +142,18 @@
 	netdev_features_t	set_features;
 #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
 			  NETIF_F_TSO6|NETIF_F_UFO)
-	struct fasync_struct	*fasync;
-
-	struct tap_filter       txflt;
-	struct socket		socket;
-	struct socket_wq	wq;
 
 	int			vnet_hdr_sz;
-
+	int			sndbuf;
+	struct tap_filter	txflt;
+	struct sock_fprog	fprog;
+	/* protected by rtnl lock */
+	bool			filter_attached;
 #ifdef TUN_DEBUG
 	int debug;
 #endif
 };
 
-struct tun_sock {
-	struct sock		sk;
-	struct tun_struct	*tun;
-};
-
-static inline struct tun_sock *tun_sk(struct sock *sk)
-{
-	return container_of(sk, struct tun_sock, sk);
-}
-
 static int tun_attach(struct tun_struct *tun, struct file *file)
 {
 	struct tun_file *tfile = file->private_data;
@@ -168,12 +172,19 @@
 		goto out;
 
 	err = 0;
+
+	/* Re-attach filter when attaching to a persist device */
+	if (tun->filter_attached == true) {
+		err = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+		if (!err)
+			goto out;
+	}
 	tfile->tun = tun;
+	tfile->socket.sk->sk_sndbuf = tun->sndbuf;
 	tun->tfile = tfile;
-	tun->socket.file = file;
 	netif_carrier_on(tun->dev);
 	dev_hold(tun->dev);
-	sock_hold(tun->socket.sk);
+	sock_hold(&tfile->sk);
 	atomic_inc(&tfile->count);
 
 out:
@@ -183,14 +194,16 @@
 
 static void __tun_detach(struct tun_struct *tun)
 {
+	struct tun_file *tfile = tun->tfile;
 	/* Detach from net device */
 	netif_tx_lock_bh(tun->dev);
 	netif_carrier_off(tun->dev);
 	tun->tfile = NULL;
+	tfile->tun = NULL;
 	netif_tx_unlock_bh(tun->dev);
 
 	/* Drop read queue */
-	skb_queue_purge(&tun->socket.sk->sk_receive_queue);
+	skb_queue_purge(&tfile->socket.sk->sk_receive_queue);
 
 	/* Drop the extra count on the net device */
 	dev_put(tun->dev);
@@ -349,21 +362,12 @@
 	/* Inform the methods they need to stop using the dev.
 	 */
 	if (tfile) {
-		wake_up_all(&tun->wq.wait);
+		wake_up_all(&tfile->wq.wait);
 		if (atomic_dec_and_test(&tfile->count))
 			__tun_detach(tun);
 	}
 }
 
-static void tun_free_netdev(struct net_device *dev)
-{
-	struct tun_struct *tun = netdev_priv(dev);
-
-	BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags));
-
-	sk_release_kernel(tun->socket.sk);
-}
-
 /* Net device open. */
 static int tun_net_open(struct net_device *dev)
 {
@@ -382,11 +386,12 @@
 static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct tun_struct *tun = netdev_priv(dev);
+	struct tun_file *tfile = tun->tfile;
 
 	tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len);
 
 	/* Drop packet if interface is not attached */
-	if (!tun->tfile)
+	if (!tfile)
 		goto drop;
 
 	/* Drop if the filter does not like it.
@@ -395,11 +400,12 @@
 	if (!check_filter(&tun->txflt, skb))
 		goto drop;
 
-	if (tun->socket.sk->sk_filter &&
-	    sk_filter(tun->socket.sk, skb))
+	if (tfile->socket.sk->sk_filter &&
+	    sk_filter(tfile->socket.sk, skb))
 		goto drop;
 
-	if (skb_queue_len(&tun->socket.sk->sk_receive_queue) >= dev->tx_queue_len) {
+	if (skb_queue_len(&tfile->socket.sk->sk_receive_queue)
+	    >= dev->tx_queue_len) {
 		if (!(tun->flags & TUN_ONE_QUEUE)) {
 			/* Normal queueing mode. */
 			/* Packet scheduler handles dropping of further packets. */
@@ -422,12 +428,12 @@
 	skb_orphan(skb);
 
 	/* Enqueue packet */
-	skb_queue_tail(&tun->socket.sk->sk_receive_queue, skb);
+	skb_queue_tail(&tfile->socket.sk->sk_receive_queue, skb);
 
 	/* Notify and wake up reader process */
-	if (tun->flags & TUN_FASYNC)
-		kill_fasync(&tun->fasync, SIGIO, POLL_IN);
-	wake_up_interruptible_poll(&tun->wq.wait, POLLIN |
+	if (tfile->flags & TUN_FASYNC)
+		kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
+	wake_up_interruptible_poll(&tfile->wq.wait, POLLIN |
 				   POLLRDNORM | POLLRDBAND);
 	return NETDEV_TX_OK;
 
@@ -555,11 +561,11 @@
 	if (!tun)
 		return POLLERR;
 
-	sk = tun->socket.sk;
+	sk = tfile->socket.sk;
 
 	tun_debug(KERN_INFO, tun, "tun_chr_poll\n");
 
-	poll_wait(file, &tun->wq.wait, wait);
+	poll_wait(file, &tfile->wq.wait, wait);
 
 	if (!skb_queue_empty(&sk->sk_receive_queue))
 		mask |= POLLIN | POLLRDNORM;
@@ -578,11 +584,11 @@
 
 /* prepad is the amount to reserve at front.  len is length after that.
  * linear is a hint as to how much to copy (usually headers). */
-static struct sk_buff *tun_alloc_skb(struct tun_struct *tun,
+static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
 				     size_t prepad, size_t len,
 				     size_t linear, int noblock)
 {
-	struct sock *sk = tun->socket.sk;
+	struct sock *sk = tfile->socket.sk;
 	struct sk_buff *skb;
 	int err;
 
@@ -682,9 +688,9 @@
 }
 
 /* Get packet from user space buffer */
-static ssize_t tun_get_user(struct tun_struct *tun, void *msg_control,
-			    const struct iovec *iv, size_t total_len,
-			    size_t count, int noblock)
+static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
+			    void *msg_control, const struct iovec *iv,
+			    size_t total_len, size_t count, int noblock)
 {
 	struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
 	struct sk_buff *skb;
@@ -754,7 +760,7 @@
 	} else
 		copylen = len;
 
-	skb = tun_alloc_skb(tun, align, copylen, gso.hdr_len, noblock);
+	skb = tun_alloc_skb(tfile, align, copylen, gso.hdr_len, noblock);
 	if (IS_ERR(skb)) {
 		if (PTR_ERR(skb) != -EAGAIN)
 			tun->dev->stats.rx_dropped++;
@@ -859,6 +865,7 @@
 {
 	struct file *file = iocb->ki_filp;
 	struct tun_struct *tun = tun_get(file);
+	struct tun_file *tfile = file->private_data;
 	ssize_t result;
 
 	if (!tun)
@@ -866,8 +873,8 @@
 
 	tun_debug(KERN_INFO, tun, "tun_chr_write %ld\n", count);
 
-	result = tun_get_user(tun, NULL, iv, iov_length(iv, count), count,
-			      file->f_flags & O_NONBLOCK);
+	result = tun_get_user(tun, tfile, NULL, iv, iov_length(iv, count),
+			      count, file->f_flags & O_NONBLOCK);
 
 	tun_put(tun);
 	return result;
@@ -875,6 +882,7 @@
 
 /* Put packet to the user space buffer */
 static ssize_t tun_put_user(struct tun_struct *tun,
+			    struct tun_file *tfile,
 			    struct sk_buff *skb,
 			    const struct iovec *iv, int len)
 {
@@ -954,7 +962,7 @@
 	return total;
 }
 
-static ssize_t tun_do_read(struct tun_struct *tun,
+static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
 			   struct kiocb *iocb, const struct iovec *iv,
 			   ssize_t len, int noblock)
 {
@@ -965,12 +973,12 @@
 	tun_debug(KERN_INFO, tun, "tun_chr_read\n");
 
 	if (unlikely(!noblock))
-		add_wait_queue(&tun->wq.wait, &wait);
+		add_wait_queue(&tfile->wq.wait, &wait);
 	while (len) {
 		current->state = TASK_INTERRUPTIBLE;
 
 		/* Read frames from the queue */
-		if (!(skb=skb_dequeue(&tun->socket.sk->sk_receive_queue))) {
+		if (!(skb = skb_dequeue(&tfile->socket.sk->sk_receive_queue))) {
 			if (noblock) {
 				ret = -EAGAIN;
 				break;
@@ -990,14 +998,14 @@
 		}
 		netif_wake_queue(tun->dev);
 
-		ret = tun_put_user(tun, skb, iv, len);
+		ret = tun_put_user(tun, tfile, skb, iv, len);
 		kfree_skb(skb);
 		break;
 	}
 
 	current->state = TASK_RUNNING;
 	if (unlikely(!noblock))
-		remove_wait_queue(&tun->wq.wait, &wait);
+		remove_wait_queue(&tfile->wq.wait, &wait);
 
 	return ret;
 }
@@ -1018,7 +1026,8 @@
 		goto out;
 	}
 
-	ret = tun_do_read(tun, iocb, iv, len, file->f_flags & O_NONBLOCK);
+	ret = tun_do_read(tun, tfile, iocb, iv, len,
+			  file->f_flags & O_NONBLOCK);
 	ret = min_t(ssize_t, ret, len);
 out:
 	tun_put(tun);
@@ -1033,7 +1042,7 @@
 	tun->group = INVALID_GID;
 
 	dev->ethtool_ops = &tun_ethtool_ops;
-	dev->destructor = tun_free_netdev;
+	dev->destructor = free_netdev;
 }
 
 /* Trivial set of netlink ops to allow deleting tun or tap
@@ -1053,7 +1062,7 @@
 
 static void tun_sock_write_space(struct sock *sk)
 {
-	struct tun_struct *tun;
+	struct tun_file *tfile;
 	wait_queue_head_t *wqueue;
 
 	if (!sock_writeable(sk))
@@ -1067,37 +1076,47 @@
 		wake_up_interruptible_sync_poll(wqueue, POLLOUT |
 						POLLWRNORM | POLLWRBAND);
 
-	tun = tun_sk(sk)->tun;
-	kill_fasync(&tun->fasync, SIGIO, POLL_OUT);
-}
-
-static void tun_sock_destruct(struct sock *sk)
-{
-	free_netdev(tun_sk(sk)->tun->dev);
+	tfile = container_of(sk, struct tun_file, sk);
+	kill_fasync(&tfile->fasync, SIGIO, POLL_OUT);
 }
 
 static int tun_sendmsg(struct kiocb *iocb, struct socket *sock,
 		       struct msghdr *m, size_t total_len)
 {
-	struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
-	return tun_get_user(tun, m->msg_control, m->msg_iov, total_len,
-			    m->msg_iovlen, m->msg_flags & MSG_DONTWAIT);
+	int ret;
+	struct tun_file *tfile = container_of(sock, struct tun_file, socket);
+	struct tun_struct *tun = __tun_get(tfile);
+
+	if (!tun)
+		return -EBADFD;
+
+	ret = tun_get_user(tun, tfile, m->msg_control, m->msg_iov, total_len,
+			   m->msg_iovlen, m->msg_flags & MSG_DONTWAIT);
+	tun_put(tun);
+	return ret;
 }
 
+
 static int tun_recvmsg(struct kiocb *iocb, struct socket *sock,
 		       struct msghdr *m, size_t total_len,
 		       int flags)
 {
-	struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
+	struct tun_file *tfile = container_of(sock, struct tun_file, socket);
+	struct tun_struct *tun = __tun_get(tfile);
 	int ret;
+
+	if (!tun)
+		return -EBADFD;
+
 	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
 		return -EINVAL;
-	ret = tun_do_read(tun, iocb, m->msg_iov, total_len,
+	ret = tun_do_read(tun, tfile, iocb, m->msg_iov, total_len,
 			  flags & MSG_DONTWAIT);
 	if (ret > total_len) {
 		m->msg_flags |= MSG_TRUNC;
 		ret = flags & MSG_TRUNC ? ret : total_len;
 	}
+	tun_put(tun);
 	return ret;
 }
 
@@ -1118,7 +1137,7 @@
 static struct proto tun_proto = {
 	.name		= "tun",
 	.owner		= THIS_MODULE,
-	.obj_size	= sizeof(struct tun_sock),
+	.obj_size	= sizeof(struct tun_file),
 };
 
 static int tun_flags(struct tun_struct *tun)
@@ -1175,8 +1194,8 @@
 
 static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 {
-	struct sock *sk;
 	struct tun_struct *tun;
+	struct tun_file *tfile = file->private_data;
 	struct net_device *dev;
 	int err;
 
@@ -1197,7 +1216,7 @@
 		     (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
 		    !capable(CAP_NET_ADMIN))
 			return -EPERM;
-		err = security_tun_dev_attach(tun->socket.sk);
+		err = security_tun_dev_attach(tfile->socket.sk);
 		if (err < 0)
 			return err;
 
@@ -1243,25 +1262,11 @@
 		tun->flags = flags;
 		tun->txflt.count = 0;
 		tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
-		set_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags);
 
-		err = -ENOMEM;
-		sk = sk_alloc(&init_net, AF_UNSPEC, GFP_KERNEL, &tun_proto);
-		if (!sk)
-			goto err_free_dev;
+		tun->filter_attached = false;
+		tun->sndbuf = tfile->socket.sk->sk_sndbuf;
 
-		sk_change_net(sk, net);
-		tun->socket.wq = &tun->wq;
-		init_waitqueue_head(&tun->wq.wait);
-		tun->socket.ops = &tun_socket_ops;
-		sock_init_data(&tun->socket, sk);
-		sk->sk_write_space = tun_sock_write_space;
-		sk->sk_sndbuf = INT_MAX;
-		sock_set_flag(sk, SOCK_ZEROCOPY);
-
-		tun_sk(sk)->tun = tun;
-
-		security_tun_dev_post_create(sk);
+		security_tun_dev_post_create(&tfile->sk);
 
 		tun_net_init(dev);
 
@@ -1271,15 +1276,13 @@
 
 		err = register_netdevice(tun->dev);
 		if (err < 0)
-			goto err_free_sk;
+			goto err_free_dev;
 
 		if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
 		    device_create_file(&tun->dev->dev, &dev_attr_owner) ||
 		    device_create_file(&tun->dev->dev, &dev_attr_group))
 			pr_err("Failed to create tun sysfs files\n");
 
-		sk->sk_destruct = tun_sock_destruct;
-
 		err = tun_attach(tun, file);
 		if (err < 0)
 			goto failed;
@@ -1311,8 +1314,6 @@
 	strcpy(ifr->ifr_name, tun->dev->name);
 	return 0;
 
- err_free_sk:
-	tun_free_netdev(dev);
  err_free_dev:
 	free_netdev(dev);
  failed:
@@ -1376,7 +1377,6 @@
 	struct tun_file *tfile = file->private_data;
 	struct tun_struct *tun;
 	void __user* argp = (void __user*)arg;
-	struct sock_fprog fprog;
 	struct ifreq ifr;
 	kuid_t owner;
 	kgid_t group;
@@ -1441,11 +1441,16 @@
 		break;
 
 	case TUNSETPERSIST:
-		/* Disable/Enable persist mode */
-		if (arg)
+		/* Disable/Enable persist mode. Keep an extra reference to the
+		 * module to prevent the module being unprobed.
+		 */
+		if (arg) {
 			tun->flags |= TUN_PERSIST;
-		else
+			__module_get(THIS_MODULE);
+		} else {
 			tun->flags &= ~TUN_PERSIST;
+			module_put(THIS_MODULE);
+		}
 
 		tun_debug(KERN_INFO, tun, "persist %s\n",
 			  arg ? "enabled" : "disabled");
@@ -1523,7 +1528,7 @@
 		break;
 
 	case TUNGETSNDBUF:
-		sndbuf = tun->socket.sk->sk_sndbuf;
+		sndbuf = tfile->socket.sk->sk_sndbuf;
 		if (copy_to_user(argp, &sndbuf, sizeof(sndbuf)))
 			ret = -EFAULT;
 		break;
@@ -1534,7 +1539,7 @@
 			break;
 		}
 
-		tun->socket.sk->sk_sndbuf = sndbuf;
+		tun->sndbuf = tfile->socket.sk->sk_sndbuf = sndbuf;
 		break;
 
 	case TUNGETVNETHDRSZ:
@@ -1562,10 +1567,12 @@
 		if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV)
 			break;
 		ret = -EFAULT;
-		if (copy_from_user(&fprog, argp, sizeof(fprog)))
+		if (copy_from_user(&tun->fprog, argp, sizeof(tun->fprog)))
 			break;
 
-		ret = sk_attach_filter(&fprog, tun->socket.sk);
+		ret = sk_attach_filter(&tun->fprog, tfile->socket.sk);
+		if (!ret)
+			tun->filter_attached = true;
 		break;
 
 	case TUNDETACHFILTER:
@@ -1573,7 +1580,9 @@
 		ret = -EINVAL;
 		if ((tun->flags & TUN_TYPE_MASK) != TUN_TAP_DEV)
 			break;
-		ret = sk_detach_filter(tun->socket.sk);
+		ret = sk_detach_filter(tfile->socket.sk);
+		if (!ret)
+			tun->filter_attached = false;
 		break;
 
 	default:
@@ -1625,27 +1634,21 @@
 
 static int tun_chr_fasync(int fd, struct file *file, int on)
 {
-	struct tun_struct *tun = tun_get(file);
+	struct tun_file *tfile = file->private_data;
 	int ret;
 
-	if (!tun)
-		return -EBADFD;
-
-	tun_debug(KERN_INFO, tun, "tun_chr_fasync %d\n", on);
-
-	if ((ret = fasync_helper(fd, file, on, &tun->fasync)) < 0)
+	if ((ret = fasync_helper(fd, file, on, &tfile->fasync)) < 0)
 		goto out;
 
 	if (on) {
 		ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);
 		if (ret)
 			goto out;
-		tun->flags |= TUN_FASYNC;
+		tfile->flags |= TUN_FASYNC;
 	} else
-		tun->flags &= ~TUN_FASYNC;
+		tfile->flags &= ~TUN_FASYNC;
 	ret = 0;
 out:
-	tun_put(tun);
 	return ret;
 }
 
@@ -1655,13 +1658,30 @@
 
 	DBG1(KERN_INFO, "tunX: tun_chr_open\n");
 
-	tfile = kmalloc(sizeof(*tfile), GFP_KERNEL);
+	tfile = (struct tun_file *)sk_alloc(&init_net, AF_UNSPEC, GFP_KERNEL,
+					    &tun_proto);
 	if (!tfile)
 		return -ENOMEM;
 	atomic_set(&tfile->count, 0);
 	tfile->tun = NULL;
 	tfile->net = get_net(current->nsproxy->net_ns);
+	tfile->flags = 0;
+
+	rcu_assign_pointer(tfile->socket.wq, &tfile->wq);
+	init_waitqueue_head(&tfile->wq.wait);
+
+	tfile->socket.file = file;
+	tfile->socket.ops = &tun_socket_ops;
+
+	sock_init_data(&tfile->socket, &tfile->sk);
+	sk_change_net(&tfile->sk, tfile->net);
+
+	tfile->sk.sk_write_space = tun_sock_write_space;
+	tfile->sk.sk_sndbuf = INT_MAX;
+
 	file->private_data = tfile;
+	set_bit(SOCK_EXTERNALLY_ALLOCATED, &tfile->socket.flags);
+
 	return 0;
 }
 
@@ -1669,6 +1689,7 @@
 {
 	struct tun_file *tfile = file->private_data;
 	struct tun_struct *tun;
+	struct net *net = tfile->net;
 
 	tun = __tun_get(tfile);
 	if (tun) {
@@ -1685,14 +1706,16 @@
 				unregister_netdevice(dev);
 			rtnl_unlock();
 		}
+
+		/* drop the reference that netdevice holds */
+		sock_put(&tfile->sk);
 	}
 
-	tun = tfile->tun;
-	if (tun)
-		sock_put(tun->socket.sk);
-
-	put_net(tfile->net);
-	kfree(tfile);
+	/* drop the reference that file holds */
+	BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED,
+			 &tfile->socket.flags));
+	sk_release_kernel(&tfile->sk);
+	put_net(net);
 
 	return 0;
 }
@@ -1820,13 +1843,14 @@
 struct socket *tun_get_socket(struct file *file)
 {
 	struct tun_struct *tun;
+	struct tun_file *tfile = file->private_data;
 	if (file->f_op != &tun_fops)
 		return ERR_PTR(-EINVAL);
 	tun = tun_get(file);
 	if (!tun)
 		return ERR_PTR(-EBADFD);
 	tun_put(tun);
-	return &tun->socket;
+	return &tfile->socket;
 }
 EXPORT_SYMBOL_GPL(tun_get_socket);