Deleting primary external storage in android multiuser framework

Question

I wanted to know how external primary storage is created and removed in multiuser android framework. When a new user is created the framework creates a folder with userid in /mnt/shell/emulated eg: /mnt/shell/emulated/10 and MediaProvider creates DCIM, Alarms etc folders inside 10 in createDefaultFolders function.

I am trying to mount this 10 folder over itself using ecryptfs when user is created so that the data written to it is encrypted. When the user is removed I unmount 10 using ecryptfs. Then when I go to /mnt/shell/emulated and list files I don't see 10 folder. But when I do mkdir 10 there it says File Exists. So I need to trace if there is an error in removing encrypted files. Which process or service removes these folders? I also noticed there is a bind mount for oob for each new user. This links /mnt/shell/emulated/obb to /mnt/shell/emulated/10/obb. This mount is done after I mount ecryptfs over /mnt/shell/emulated/10 which means that obb mount point will also b encrypted. I am not sure if this is interfering with the folder removal process. How do I track where the removal is failing?