nvmeof: refactor gateway connection pattern for ControllerModifyVolume

Extracted common gateway connection logic
into `withGatewayConnection()` helper to avoid code duplication
between QoS and host management operations (in the next commit).

The helper manages:
- Secret retrieval
- NVMe-oF metadata extraction from volume
- Gateway connection with automatic cleanup
- Operation execution via callback function
Refactored modifyNVMeoFQoS to use the new helper.

Signed-off-by: gadi-didi <gadi.didi@ibm.com>

Author: gadididi

internal/nvmeof/controller/controllerserver.go

@@ -353,7 +353,9 @@ func (cs *Server) ControllerModifyVolume(
 		return nil, status.Errorf(codes.InvalidArgument, "failed to parse QoS parameters: %v", err)
 	}
 	if nvmeofQoS != nil {
-		return cs.modifyNVMeoFQoS(ctx, req, nvmeofQoS)
+		if err := cs.modifyNVMeoFQoS(ctx, req, nvmeofQoS); err != nil {
+			return nil, err
+		}
 	}
 
 	return &csi.ControllerModifyVolumeResponse{}, nil
@@ -568,34 +570,32 @@ func parseQoSParameters(params map[string]string) (*nvmeof.NVMeoFQosVolume, erro
 	return qos, nil
 }
 
-// modifyNVMeoFQoS handles NVMe-oF gateway QoS modification.
-func (cs *Server) modifyNVMeoFQoS(
+// withGatewayConnection is a helper that manages the common pattern of:
+// 1. Getting secrets (with fallback to k8s secret)
+// 2. Getting NVMe-oF metadata
+// 3. Connecting to gateway with proper cleanup
+// 4. Executing the provided operation function.
+func (cs *Server) withGatewayConnection(
 	ctx context.Context,
 	req *csi.ControllerModifyVolumeRequest,
-	qos *nvmeof.NVMeoFQosVolume,
-) (*csi.ControllerModifyVolumeResponse, error) {
-	volumeID := req.GetVolumeId()
-
+	volumeID string,
+	fn func(context.Context, *nvmeof.GatewayRpcClient, *nvmeof.NVMeoFVolumeData) error,
+) error {
 	// Step 1: Get secrets
-
-	// Since ControllerModifyVolume doesn't receive volume context and dont have option to take secrets
-	// because there is no "csi.storage.k8s.io/controller-modify-secret-name" field in the SC !,
-	// the full solution for it is to use GetControllerExpandSecretRef but there is no such function yet.
-	// TODO: change the call to GetControllerExpandSecretRef once it is implemented.
 	secrets := req.GetSecrets()
 	if secrets == nil {
 		secretName, secretNamespace, err := util.GetControllerPublishSecretRef(volumeID, util.RBDType)
 		if err != nil {
 			log.ErrorLog(ctx, "Failed to get secret reference: %v", err)
 
-			return nil, status.Errorf(codes.Internal, "failed to get secret reference: %v", err)
+			return status.Errorf(codes.Internal, "failed to get secret reference: %v", err)
 		}
 
 		secrets, err = k8s.GetSecret(secretName, secretNamespace)
 		if err != nil {
 			log.ErrorLog(ctx, "Failed to get secret from k8s: %v", err)
 
-			return nil, status.Errorf(codes.Internal, "failed to get secret: %v", err)
+			return status.Errorf(codes.Internal, "failed to get secret: %v", err)
 		}
 	}
 
@@ -604,7 +604,7 @@ func (cs *Server) modifyNVMeoFQoS(
 	if err != nil {
 		log.ErrorLog(ctx, "Failed to get NVMe-oF metadata: %v", err)
 
-		return nil, nvmeoferrors.ToGRPCError(err)
+		return nvmeoferrors.ToGRPCError(err)
 	}
 
 	// Step 3: Connect to gateway
@@ -616,35 +616,52 @@ func (cs *Server) modifyNVMeoFQoS(
 	if err != nil {
 		log.ErrorLog(ctx, "Gateway connection failed: %v", err)
 
-		return nil, status.Errorf(codes.Unavailable, "gateway connection failed: %v", err)
+		return status.Errorf(codes.Unavailable, "gateway connection failed: %v", err)
 	}
 	defer func() {
 		if closeErr := gateway.Destroy(); closeErr != nil {
 			log.ErrorLog(ctx, "Failed to close gateway connection: %v", closeErr)
 		}
 	}()
 
-	// Step 4: Apply NVMe-oF QoS via gateway
-	log.DebugLog(ctx, "Setting QoS for subsystem=%s, nsid=%d", nvmeofData.SubsystemNQN, nvmeofData.NamespaceID)
+	// Step 4: Execute the operation
+	return fn(ctx, gateway, nvmeofData)
+}
 
-	err = gateway.SetQoSLimitsForNamespace(ctx, nvmeofData.SubsystemNQN, nvmeofData.NamespaceID, *qos)
-	if err != nil {
-		// Check if error is EEXIST (RBD QoS already set)
-		if errors.Is(err, nvmeoferrors.ErrRbdQoSExists) {
-			log.ErrorLog(ctx, "RBD QoS already configured on volume")
+// modifyNVMeoFQoS handles NVMe-oF gateway QoS modification.
+func (cs *Server) modifyNVMeoFQoS(
+	ctx context.Context,
+	req *csi.ControllerModifyVolumeRequest,
+	qos *nvmeof.NVMeoFQosVolume,
+) error {
+	volumeID := req.GetVolumeId()
 
-			return nil, status.Error(codes.InvalidArgument,
-				"RBD QoS already configured on this volume, cannot set NVMe-oF gateway QoS")
-		}
+	return cs.withGatewayConnection(ctx, req, volumeID, func(
+		ctx context.Context,
+		gateway *nvmeof.GatewayRpcClient,
+		nvmeofData *nvmeof.NVMeoFVolumeData,
+	) error {
+		log.DebugLog(ctx, "Setting QoS for subsystem=%s, nsid=%d", nvmeofData.SubsystemNQN, nvmeofData.NamespaceID)
 
-		log.ErrorLog(ctx, "Failed to set QoS limits: %v", err)
+		err := gateway.SetQoSLimitsForNamespace(ctx, nvmeofData.SubsystemNQN, nvmeofData.NamespaceID, *qos)
+		if err != nil {
+			// Check if error is EEXIST (RBD QoS already set)
+			if errors.Is(err, nvmeoferrors.ErrRbdQoSExists) {
+				log.ErrorLog(ctx, "RBD QoS already configured on volume")
 
-		return nil, status.Errorf(codes.Internal, "failed to set QoS limits: %v", err)
-	}
+				return status.Error(codes.InvalidArgument,
+					"RBD QoS already configured on this volume, cannot set NVMe-oF gateway QoS")
+			}
 
-	log.DebugLog(ctx, "Successfully modified NVMe-oF QoS for volume %s", volumeID)
+			log.ErrorLog(ctx, "Failed to set QoS limits: %v", err)
 
-	return &csi.ControllerModifyVolumeResponse{}, nil
+			return status.Errorf(codes.Internal, "failed to set QoS limits: %v", err)
+		}
+
+		log.DebugLog(ctx, "Successfully modified NVMe-oF QoS for volume %s", volumeID)
+
+		return nil
+	})
 }
 
 // ensureSubsystem checks if the subsystem exists, and creates it if not.