Staging: hv: storvsc: Introduce state to manage the lifecycle of stor device

Introduce state to manage the lifecycle of stor device. This would be the
basis for managing the references on the stor object.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/hyperv_storage.h

@@ -266,7 +266,7 @@ struct storvsc_device {
 
 	/* 0 indicates the device is being destroyed */
 	atomic_t ref_count;
-
+	bool	 destroy;
 	bool	 drain_notify;
 	atomic_t num_outstanding_req;
 

drivers/staging/hv/storvsc.c

@@ -43,7 +43,7 @@ static inline struct storvsc_device *alloc_stor_device(struct hv_device *device)
 	/* Set to 2 to allow both inbound and outbound traffics */
 	/* (ie get_out_stor_device() and get_in_stor_device()) to proceed. */
 	atomic_set(&stor_device->ref_count, 2);
-
+	stor_device->destroy = false;
 	init_waitqueue_head(&stor_device->waiting_to_drain);
 	stor_device->device = device;
 	device->ext = stor_device;
@@ -399,9 +399,15 @@ int storvsc_dev_add(struct hv_device *device,
 int storvsc_dev_remove(struct hv_device *device)
 {
 	struct storvsc_device *stor_device;
+	unsigned long flags;
+
 
 	stor_device = release_stor_device(device);
 
+	spin_lock_irqsave(&device->channel->inbound_lock, flags);
+	stor_device->destroy = true;
+	spin_unlock_irqrestore(&device->channel->inbound_lock, flags);
+
 	/*
 	 * At this point, all outbound traffic should be disable. We
 	 * only allow inbound traffic (responses) to proceed so that