[SCSI] storvsc: Implement multi-channel support

Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: NHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

drivers/scsi/storvsc_drv.c

@@ -328,6 +328,8 @@ static int storvsc_timeout = 180;
 
 #define STORVSC_MAX_IO_REQUESTS				128
 
+static void storvsc_on_channel_callback(void *context);
+
 /*
  * In Hyper-V, each port/path/target maps to 1 scsi host adapter.  In
  * reality, the path/target is not used (ie always set to 0) so our
@@ -364,6 +366,7 @@ struct storvsc_device {
 
 	bool	 destroy;
 	bool	 drain_notify;
+	bool	 open_sub_channel;
 	atomic_t num_outstanding_req;
 	struct Scsi_Host *host;
 
@@ -755,12 +758,104 @@ static unsigned int copy_to_bounce_buffer(struct scatterlist *orig_sgl,
 	return total_copied;
 }
 
+static void handle_sc_creation(struct vmbus_channel *new_sc)
+{
+	struct hv_device *device = new_sc->primary_channel->device_obj;
+	struct storvsc_device *stor_device;
+	struct vmstorage_channel_properties props;
+
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	if (stor_device->open_sub_channel == false)
+		return;
+
+	memset(&props, 0, sizeof(struct vmstorage_channel_properties));
+
+	vmbus_open(new_sc,
+		   storvsc_ringbuffer_size,
+		   storvsc_ringbuffer_size,
+		   (void *)&props,
+		   sizeof(struct vmstorage_channel_properties),
+		   storvsc_on_channel_callback, new_sc);
+}
+
+static void  handle_multichannel_storage(struct hv_device *device, int max_chns)
+{
+	struct storvsc_device *stor_device;
+	int num_cpus = num_online_cpus();
+	int num_sc;
+	struct storvsc_cmd_request *request;
+	struct vstor_packet *vstor_packet;
+	int ret, t;
+
+	num_sc = ((max_chns > num_cpus) ? num_cpus : max_chns);
+	stor_device = get_out_stor_device(device);
+	if (!stor_device)
+		return;
+
+	request = &stor_device->init_request;
+	vstor_packet = &request->vstor_packet;
+
+	stor_device->open_sub_channel = true;
+	/*
+	 * Establish a handler for dealing with subchannels.
+	 */
+	vmbus_set_sc_create_callback(device->channel, handle_sc_creation);
+
+	/*
+	 * Check to see if sub-channels have already been created. This
+	 * can happen when this driver is re-loaded after unloading.
+	 */
+
+	if (vmbus_are_subchannels_present(device->channel))
+		return;
+
+	stor_device->open_sub_channel = false;
+	/*
+	 * Request the host to create sub-channels.
+	 */
+	memset(request, 0, sizeof(struct storvsc_cmd_request));
+	init_completion(&request->wait_event);
+	vstor_packet->operation = VSTOR_OPERATION_CREATE_SUB_CHANNELS;
+	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
+	vstor_packet->sub_channel_count = num_sc;
+
+	ret = vmbus_sendpacket(device->channel, vstor_packet,
+			       (sizeof(struct vstor_packet) -
+			       vmscsi_size_delta),
+			       (unsigned long)request,
+			       VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+
+	if (ret != 0)
+		return;
+
+	t = wait_for_completion_timeout(&request->wait_event, 10*HZ);
+	if (t == 0)
+		return;
+
+	if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
+	    vstor_packet->status != 0)
+		return;
+
+	/*
+	 * Now that we created the sub-channels, invoke the check; this
+	 * may trigger the callback.
+	 */
+	stor_device->open_sub_channel = true;
+	vmbus_are_subchannels_present(device->channel);
+}
+
 static int storvsc_channel_init(struct hv_device *device)
 {
 	struct storvsc_device *stor_device;
 	struct storvsc_cmd_request *request;
 	struct vstor_packet *vstor_packet;
 	int ret, t;
+	int max_chns;
+	bool process_sub_channels = false;
 
 	stor_device = get_out_stor_device(device);
 	if (!stor_device)
@@ -855,6 +950,19 @@ static int storvsc_channel_init(struct hv_device *device)
 	    vstor_packet->status != 0)
 		goto cleanup;
 
+	/*
+	 * Check to see if multi-channel support is there.
+	 * Hosts that implement protocol version of 5.1 and above
+	 * support multi-channel.
+	 */
+	max_chns = vstor_packet->storage_channel_properties.max_channel_cnt;
+	if ((vmbus_proto_version != VERSION_WIN7) &&
+	   (vmbus_proto_version != VERSION_WS2008))  {
+		if (vstor_packet->storage_channel_properties.flags &
+		    STORAGE_CHANNEL_SUPPORTS_MULTI_CHANNEL)
+			process_sub_channels = true;
+	}
+
 	memset(vstor_packet, 0, sizeof(struct vstor_packet));
 	vstor_packet->operation = VSTOR_OPERATION_END_INITIALIZATION;
 	vstor_packet->flags = REQUEST_COMPLETION_FLAG;
@@ -879,6 +987,9 @@ static int storvsc_channel_init(struct hv_device *device)
 	    vstor_packet->status != 0)
 		goto cleanup;
 
+	if (process_sub_channels)
+		handle_multichannel_storage(device, max_chns);
+
 
 cleanup:
 	return ret;
@@ -1100,7 +1211,8 @@ static void storvsc_on_receive(struct hv_device *device,
 
 static void storvsc_on_channel_callback(void *context)
 {
-	struct hv_device *device = (struct hv_device *)context;
+	struct vmbus_channel *channel = (struct vmbus_channel *)context;
+	struct hv_device *device;
 	struct storvsc_device *stor_device;
 	u32 bytes_recvd;
 	u64 request_id;
@@ -1108,13 +1220,17 @@ static void storvsc_on_channel_callback(void *context)
 	struct storvsc_cmd_request *request;
 	int ret;
 
+	if (channel->primary_channel != NULL)
+		device = channel->primary_channel->device_obj;
+	else
+		device = channel->device_obj;
 
 	stor_device = get_in_stor_device(device);
 	if (!stor_device)
 		return;
 
 	do {
-		ret = vmbus_recvpacket(device->channel, packet,
+		ret = vmbus_recvpacket(channel, packet,
 				       ALIGN((sizeof(struct vstor_packet) -
 					     vmscsi_size_delta), 8),
 				       &bytes_recvd, &request_id);
@@ -1155,7 +1271,7 @@ static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size)
 			 ring_size,
 			 (void *)&props,
 			 sizeof(struct vmstorage_channel_properties),
-			 storvsc_on_channel_callback, device);
+			 storvsc_on_channel_callback, device->channel);
 
 	if (ret != 0)
 		return ret;
@@ -1207,6 +1323,7 @@ static int storvsc_do_io(struct hv_device *device,
 {
 	struct storvsc_device *stor_device;
 	struct vstor_packet *vstor_packet;
+	struct vmbus_channel *outgoing_channel;
 	int ret = 0;
 
 	vstor_packet = &request->vstor_packet;
@@ -1217,6 +1334,11 @@ static int storvsc_do_io(struct hv_device *device,
 
 
 	request->device  = device;
+	/*
+	 * Select an an appropriate channel to send the request out.
+	 */
+
+	outgoing_channel = vmbus_get_outgoing_channel(device->channel);
 
 
 	vstor_packet->flags |= REQUEST_COMPLETION_FLAG;
@@ -1234,7 +1356,7 @@ static int storvsc_do_io(struct hv_device *device,
 	vstor_packet->operation = VSTOR_OPERATION_EXECUTE_SRB;
 
 	if (request->data_buffer.len) {
-		ret = vmbus_sendpacket_multipagebuffer(device->channel,
+		ret = vmbus_sendpacket_multipagebuffer(outgoing_channel,
 				&request->data_buffer,
 				vstor_packet,
 				(sizeof(struct vstor_packet) -
@@ -1643,6 +1765,7 @@ static int storvsc_probe(struct hv_device *device,
 	}
 
 	stor_device->destroy = false;
+	stor_device->open_sub_channel = false;
 	init_waitqueue_head(&stor_device->waiting_to_drain);
 	stor_device->device = device;
 	stor_device->host = host;