Drivers: hv: utils: Continue to poll VSS channel after handling requests.

BugLink: http://bugs.launchpad.net/bugs/1650059

Multiple VSS_OP_HOT_BACKUP requests may arrive in quick succession, even
though the host only signals once. The driver wass handling the first
request while ignoring the others in the ring buffer. We should poll the
VSS channel after handling a request to continue processing other requests.
Signed-off-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 497af84b)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/hv/hv_snapshot.c

@@ -67,11 +67,11 @@ static const char vss_devname[] = "vmbus/hv_vss";
 static __u8 *recv_buffer;
 static struct hvutil_transport *hvt;
 
-static void vss_send_op(struct work_struct *dummy);
 static void vss_timeout_func(struct work_struct *dummy);
+static void vss_handle_request(struct work_struct *dummy);
 
 static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
-static DECLARE_WORK(vss_send_op_work, vss_send_op);
+static DECLARE_WORK(vss_handle_request_work, vss_handle_request);
 
 static void vss_poll_wrapper(void *channel)
 {
@@ -156,8 +156,7 @@ static int vss_on_msg(void *msg, int len)
 	return 0;
 }
 
-
-static void vss_send_op(struct work_struct *dummy)
+static void vss_send_op(void)
 {
 	int op = vss_transaction.msg->vss_hdr.operation;
 	int rc;
@@ -174,6 +173,9 @@ static void vss_send_op(struct work_struct *dummy)
 	vss_msg->vss_hdr.operation = op;
 
 	vss_transaction.state = HVUTIL_USERSPACE_REQ;
+
+	schedule_delayed_work(&vss_timeout_work, VSS_USERSPACE_TIMEOUT);
+
 	rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
 	if (rc) {
 		pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
@@ -188,6 +190,40 @@ static void vss_send_op(struct work_struct *dummy)
 	return;
 }
 
+static void vss_handle_request(struct work_struct *dummy)
+{
+	switch (vss_transaction.msg->vss_hdr.operation) {
+	/*
+	 * Initiate a "freeze/thaw" operation in the guest.
+	 * We respond to the host once the operation is complete.
+	 *
+	 * We send the message to the user space daemon and the operation is
+	 * performed in the daemon.
+	 */
+	case VSS_OP_THAW:
+	case VSS_OP_FREEZE:
+		if (vss_transaction.state < HVUTIL_READY) {
+			/* Userspace is not registered yet */
+			vss_respond_to_host(HV_E_FAIL);
+			return;
+		}
+		vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
+		vss_send_op();
+		return;
+	case VSS_OP_HOT_BACKUP:
+		vss_transaction.msg->vss_cf.flags = VSS_HBU_NO_AUTO_RECOVERY;
+		break;
+	case VSS_OP_GET_DM_INFO:
+		vss_transaction.msg->dm_info.flags = 0;
+		break;
+	default:
+		break;
+	}
+
+	vss_respond_to_host(0);
+	hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
+}
+
 /*
  * Send a response back to the host.
  */
@@ -272,48 +308,8 @@ void hv_vss_onchannelcallback(void *context)
 			vss_transaction.recv_req_id = requestid;
 			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 
-			switch (vss_msg->vss_hdr.operation) {
-				/*
-				 * Initiate a "freeze/thaw"
-				 * operation in the guest.
-				 * We respond to the host once
-				 * the operation is complete.
-				 *
-				 * We send the message to the
-				 * user space daemon and the
-				 * operation is performed in
-				 * the daemon.
-				 */
-			case VSS_OP_FREEZE:
-			case VSS_OP_THAW:
-				if (vss_transaction.state < HVUTIL_READY) {
-					/* Userspace is not registered yet */
-					vss_respond_to_host(HV_E_FAIL);
-					return;
-				}
-				vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
-				schedule_work(&vss_send_op_work);
-				schedule_delayed_work(&vss_timeout_work,
-						      VSS_USERSPACE_TIMEOUT);
-				return;
-
-			case VSS_OP_HOT_BACKUP:
-				vss_msg->vss_cf.flags =
-					 VSS_HBU_NO_AUTO_RECOVERY;
-				vss_respond_to_host(0);
-				return;
-
-			case VSS_OP_GET_DM_INFO:
-				vss_msg->dm_info.flags = 0;
-				vss_respond_to_host(0);
-				return;
-
-			default:
-				vss_respond_to_host(0);
-				return;
-
-			}
-
+			schedule_work(&vss_handle_request_work);
+			return;
 		}
 
 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
@@ -364,6 +360,6 @@ void hv_vss_deinit(void)
 {
 	vss_transaction.state = HVUTIL_DEVICE_DYING;
 	cancel_delayed_work_sync(&vss_timeout_work);
-	cancel_work_sync(&vss_send_op_work);
+	cancel_work_sync(&vss_handle_request_work);
 	hvutil_transport_destroy(hvt);
 }