Use repeated usage for representing volume stats

Author: gnufied

csi.proto

@@ -1027,49 +1027,36 @@ message NodeGetVolumeStatsRequest {
   // The ID of the volume. This field is REQUIRED.
   string volume_id = 1;
 
-  // The path at which the volume was published. It MUST be an absolute
-  // path in the root filesystem of the process serving this request.
+  // It can be any valid path where volume was previously published.
+  // It MUST be an absolute path in the root filesystem of
+  // the process serving this request.
   // This is a REQUIRED field.
-  string target_path = 2;
+  string volume_path = 2;
 }
 
 message NodeGetVolumeStatsResponse {
-  // The used capacity in bytes. This field is OPTIONAL.
-  // The value of this field MUST NOT be negative.
-  // For volumes that share a filesystem with the host (e.g hostpath)
-  // this is used space on the underlying storage by specified
-  // shared path or directory.
-  int64 used_capacity = 1;
-
-  // The available capacity in bytes. This field is OPTIONAL.
-  // For volumes that share a filesystem with the host (e.g hostpath)
-  // this is available space on the underlying storage and is
-  // shared with the host processes and other volumes.
-  // The value of this field MUST NOT be negative.
-  int64 available_capacity = 2;
+  repeated VolumeUsage usage = 1;
+}
 
-  // The total capacity in bytes. This field is REQUIRED.
-  // For volumes that share a file system with the host (e.g hostpath)
-  // this is the total size of underlying storage and it MAY
-  // not be equal to used_capacity + available_capacity because
-  // filesystem is shared.
+message VolumeUsage {
+  enum Unit {
+    BYTES = 0;
+    INODES = 1;
+  }
+  // The available capacity in specified Unit. This field is OPTIONAL.
   // The value of this field MUST NOT be negative.
-  int64 total_capacity = 3;
+  int64 available = 1;
 
-  // The number of inodes used by the volume.
-  // This field is OPTIONAL.
+  // The total capacity in specified Unit. This field is REQUIRED.
   // The value of this field MUST NOT be negative.
-  int64 used_inodes = 4;
+  int64 total = 2;
 
-  // The total number of inodes on the underlying filesystem.
-  // This field is OPTIONAL
+  // The used capacity in specified Unit. This field is OPTIONAL.
   // The value of this field MUST NOT be negative.
-  int64 total_inodes = 5;
+  int64 used = 3;
 
-  // The total number of free inodes on the underlying filesystem.
-  // This field is OPTIONAL.
-  // The value of this field MUST NOT be negative.
-  int64 available_inodes = 6;
+  // The units that represent this value
+  Unit unit = 4;
 }
 message NodeGetIdRequest {
   // Intentionally empty.
@@ -1097,6 +1084,10 @@ message NodeServiceCapability {
     enum Type {
       UNKNOWN = 0;
       STAGE_UNSTAGE_VOLUME = 1;
+      // If Plugin implements GET_VOLUME_STATS capability
+      // then it MUST implement NodeGetVolumeStats RPC
+      // call for fetching volume stats
+      GET_VOLUME_STATS = 2;
     }
 
     Type type = 1;