signal to release an fd?

[Stef Bon]

Well, this issue does not only happen with a construction like mine.

For example, when working on a document on a USB stick (or a partition
on a harddisk)  with
LibreOffice for example, and you want to create another filesystem on it.

It's a very good and gentle service to the average user to have a
mechanism which informs the app to do something, like for example a
dialog informing the user and asking what to do.

You as developer will probably not need this, but I think this is
something for normal users.

Stef