Drivers: hv: vmbus: add a per-channel rescind callback

This will be used by the coming hv_sock driver.
Signed-off-by: NDexuan Cui <decui@microsoft.com>
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel_mgmt.c

@@ -741,6 +741,10 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 	spin_unlock_irqrestore(&channel->lock, flags);
 
 	if (channel->device_obj) {
+		if (channel->chn_rescind_callback) {
+			channel->chn_rescind_callback(channel);
+			return;
+		}
 		/*
 		 * We will have to unregister this device from the
 		 * driver core.
@@ -1110,3 +1114,10 @@ bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);
+
+void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
+		void (*chn_rescind_cb)(struct vmbus_channel *))
+{
+	channel->chn_rescind_callback = chn_rescind_cb;
+}
+EXPORT_SYMBOL_GPL(vmbus_set_chn_rescind_callback);

include/linux/hyperv.h

@@ -765,6 +765,12 @@ struct vmbus_channel {
 	 */
 	void (*sc_creation_callback)(struct vmbus_channel *new_sc);
 
+	/*
+	 * Channel rescind callback. Some channels (the hvsock ones), need to
+	 * register a callback which is invoked in vmbus_onoffer_rescind().
+	 */
+	void (*chn_rescind_callback)(struct vmbus_channel *channel);
+
 	/*
 	 * The spinlock to protect the structure. It is being used to protect
 	 * test-and-set access to various attributes of the structure as well
@@ -851,6 +857,9 @@ int vmbus_request_offers(void);
 void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
 			void (*sc_cr_cb)(struct vmbus_channel *new_sc));
 
+void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
+		void (*chn_rescind_cb)(struct vmbus_channel *));
+
 /*
  * Retrieve the (sub) channel on which to send an outgoing request.
  * When a primary channel has multiple sub-channels, we choose a