Allow modifying volume topology

Author: iltyty

csi.proto

@@ -1041,10 +1041,44 @@ message ControllerModifyVolumeRequest {
   // on the absence of keys, only keys that are specified should result
   // in modifications to the volume.
   map<string, string> mutable_parameters = 3;
+
+  // Indicates whether the CO allows the SP to update the topology
+  // as part of the modification.
+  bool allow_topology_updates = 4;
 }
 
 message ControllerModifyVolumeResponse {
   option (alpha_message) = true;
+
+  // Specifies where (regions, zones, racks, etc.) the modified
+  // volume is accessible from.
+  // A plugin that returns this field MUST also set the
+  // VOLUME_ACCESSIBILITY_CONSTRAINTS plugin capability.
+  // An SP MAY specify multiple topologies to indicate the volume is
+  // accessible from multiple locations.
+  // COs MAY use this information along with the topology information
+  // returned by NodeGetInfo to ensure that a given volume is accessible
+  // from a given node when scheduling workloads.
+  // This field is OPTIONAL. It is effective to replace the
+  // accessible_topology returned by CreateVolume if the plugin has
+  // MODIFY_VOLUME_TOPOLOGY controller capability.
+  // If it is not specified, the CO MAY assume
+  // the volume is equally accessible from all nodes in the cluster and
+  // MAY schedule workloads referencing the volume on any available
+  // node. 
+  //
+  // SP MUST only set this field if allow_topology_updates is set
+  // in the request. SP SHOULD fail the request if it needs to update
+  // topology but is not allowed by CO.
+  repeated Topology accessible_topology = 1;
+
+  // Indicates whether the modification is still in progress.
+  // SPs MAY set in_progress to update the accessible_topology
+  // before the modification finishes to reduce possible race
+  // conditions.
+  // COs SHOULD retry the request if in_progress is set to true,
+  // until in_progress is set to false.
+  bool in_progress = 2;
 }
 
 message GetCapacityRequest {
@@ -1194,6 +1228,10 @@ message ControllerServiceCapability {
       // Indicates the SP supports the GetSnapshot RPC.
       // This enables COs to fetch an existing snapshot.
       GET_SNAPSHOT = 15 [(alpha_enum_value) = true];
+
+      // Indicates the SP supports modifying volume topology.
+      // See ControllerModifyVolume for details.
+      MODIFY_VOLUME_TOPOLOGY = 16 [(alpha_enum_value) = true];
     }
 
     Type type = 1;