--- /dev/null
+From a9eeb998c28d5506616426bd3a216bd5735a18b8 Mon Sep 17 00:00:00 2001
+From: Sunil Muthuswamy <sunilmut@microsoft.com>
+Date: Wed, 15 May 2019 00:56:05 +0000
+Subject: hv_sock: Add support for delayed close
+
+From: Sunil Muthuswamy <sunilmut@microsoft.com>
+
+commit a9eeb998c28d5506616426bd3a216bd5735a18b8 upstream.
+
+Currently, hvsock does not implement any delayed or background close
+logic. Whenever the hvsock socket is closed, a FIN is sent to the peer, and
+the last reference to the socket is dropped, which leads to a call to
+.destruct where the socket can hang indefinitely waiting for the peer to
+close it's side. The can cause the user application to hang in the close()
+call.
+
+This change implements proper STREAM(TCP) closing handshake mechanism by
+sending the FIN to the peer and the waiting for the peer's FIN to arrive
+for a given timeout. On timeout, it will try to terminate the connection
+(i.e. a RST). This is in-line with other socket providers such as virtio.
+
+This change does not address the hang in the vmbus_hvsock_device_unregister
+where it waits indefinitely for the host to rescind the channel. That
+should be taken up as a separate fix.
+
+Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
+Reviewed-by: Dexuan Cui <decui@microsoft.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ net/vmw_vsock/hyperv_transport.c | 110 +++++++++++++++++++++++++++------------
+ 1 file changed, 78 insertions(+), 32 deletions(-)
+
+--- a/net/vmw_vsock/hyperv_transport.c
++++ b/net/vmw_vsock/hyperv_transport.c
+@@ -35,6 +35,9 @@
+ /* The MTU is 16KB per the host side's design */
+ #define HVS_MTU_SIZE (1024 * 16)
+
++/* How long to wait for graceful shutdown of a connection */
++#define HVS_CLOSE_TIMEOUT (8 * HZ)
++
+ struct vmpipe_proto_header {
+ u32 pkt_type;
+ u32 data_size;
+@@ -290,19 +293,32 @@ static void hvs_channel_cb(void *ctx)
+ sk->sk_write_space(sk);
+ }
+
+-static void hvs_close_connection(struct vmbus_channel *chan)
++static void hvs_do_close_lock_held(struct vsock_sock *vsk,
++ bool cancel_timeout)
+ {
+- struct sock *sk = get_per_channel_state(chan);
+- struct vsock_sock *vsk = vsock_sk(sk);
+-
+- lock_sock(sk);
++ struct sock *sk = sk_vsock(vsk);
+
+- sk->sk_state = TCP_CLOSE;
+ sock_set_flag(sk, SOCK_DONE);
+- vsk->peer_shutdown |= SEND_SHUTDOWN | RCV_SHUTDOWN;
+-
++ vsk->peer_shutdown = SHUTDOWN_MASK;
++ if (vsock_stream_has_data(vsk) <= 0)
++ sk->sk_state = TCP_CLOSING;
+ sk->sk_state_change(sk);
++ if (vsk->close_work_scheduled &&
++ (!cancel_timeout || cancel_delayed_work(&vsk->close_work))) {
++ vsk->close_work_scheduled = false;
++ vsock_remove_sock(vsk);
++
++ /* Release the reference taken while scheduling the timeout */
++ sock_put(sk);
++ }
++}
++
++static void hvs_close_connection(struct vmbus_channel *chan)
++{
++ struct sock *sk = get_per_channel_state(chan);
+
++ lock_sock(sk);
++ hvs_do_close_lock_held(vsock_sk(sk), true);
+ release_sock(sk);
+ }
+
+@@ -446,50 +462,80 @@ static int hvs_connect(struct vsock_sock
+ return vmbus_send_tl_connect_request(&h->vm_srv_id, &h->host_srv_id);
+ }
+
++static void hvs_shutdown_lock_held(struct hvsock *hvs, int mode)
++{
++ struct vmpipe_proto_header hdr;
++
++ if (hvs->fin_sent || !hvs->chan)
++ return;
++
++ /* It can't fail: see hvs_channel_writable_bytes(). */
++ (void)hvs_send_data(hvs->chan, (struct hvs_send_buf *)&hdr, 0);
++ hvs->fin_sent = true;
++}
++
+ static int hvs_shutdown(struct vsock_sock *vsk, int mode)
+ {
+ struct sock *sk = sk_vsock(vsk);
+- struct vmpipe_proto_header hdr;
+- struct hvs_send_buf *send_buf;
+- struct hvsock *hvs;
+
+ if (!(mode & SEND_SHUTDOWN))
+ return 0;
+
+ lock_sock(sk);
+-
+- hvs = vsk->trans;
+- if (hvs->fin_sent)
+- goto out;
+-
+- send_buf = (struct hvs_send_buf *)&hdr;
+-
+- /* It can't fail: see hvs_channel_writable_bytes(). */
+- (void)hvs_send_data(hvs->chan, send_buf, 0);
+-
+- hvs->fin_sent = true;
+-out:
++ hvs_shutdown_lock_held(vsk->trans, mode);
+ release_sock(sk);
+ return 0;
+ }
+
+-static void hvs_release(struct vsock_sock *vsk)
++static void hvs_close_timeout(struct work_struct *work)
+ {
++ struct vsock_sock *vsk =
++ container_of(work, struct vsock_sock, close_work.work);
+ struct sock *sk = sk_vsock(vsk);
+- struct hvsock *hvs = vsk->trans;
+- struct vmbus_channel *chan;
+
++ sock_hold(sk);
+ lock_sock(sk);
++ if (!sock_flag(sk, SOCK_DONE))
++ hvs_do_close_lock_held(vsk, false);
+
+- sk->sk_state = TCP_CLOSING;
+- vsock_remove_sock(vsk);
+-
++ vsk->close_work_scheduled = false;
+ release_sock(sk);
++ sock_put(sk);
++}
+
+- chan = hvs->chan;
+- if (chan)
+- hvs_shutdown(vsk, RCV_SHUTDOWN | SEND_SHUTDOWN);
++/* Returns true, if it is safe to remove socket; false otherwise */
++static bool hvs_close_lock_held(struct vsock_sock *vsk)
++{
++ struct sock *sk = sk_vsock(vsk);
++
++ if (!(sk->sk_state == TCP_ESTABLISHED ||
++ sk->sk_state == TCP_CLOSING))
++ return true;
++
++ if ((sk->sk_shutdown & SHUTDOWN_MASK) != SHUTDOWN_MASK)
++ hvs_shutdown_lock_held(vsk->trans, SHUTDOWN_MASK);
++
++ if (sock_flag(sk, SOCK_DONE))
++ return true;
++
++ /* This reference will be dropped by the delayed close routine */
++ sock_hold(sk);
++ INIT_DELAYED_WORK(&vsk->close_work, hvs_close_timeout);
++ vsk->close_work_scheduled = true;
++ schedule_delayed_work(&vsk->close_work, HVS_CLOSE_TIMEOUT);
++ return false;
++}
+
++static void hvs_release(struct vsock_sock *vsk)
++{
++ struct sock *sk = sk_vsock(vsk);
++ bool remove_sock;
++
++ lock_sock(sk);
++ remove_sock = hvs_close_lock_held(vsk);
++ release_sock(sk);
++ if (remove_sock)
++ vsock_remove_sock(vsk);
+ }
+
+ static void hvs_destruct(struct vsock_sock *vsk)