Merge pull request #17649 from rsmoorthy/rsmoorthy-patch-1

volume plugin doc update

docs/extend/plugins_volume.md

@@ -101,7 +101,9 @@ Respond with a string error if an error occurred.
 ```
 
 Docker requires the plugin to provide a volume, given a user specified volume
-name. This is called once per container start.
+name. This is called once per container start. If the same volume_name is requested
+more than once, the plugin may need to keep track of each new mount request and provision
+at the first mount request and deprovision at the last corresponding unmount request.
 
 **Response**:
 ```