Re: What happens to mappings when closing file?

[Marcus Brinkmann]

olafBuddenhagen@gmx.net wrote:
> Hi,
> 
> I'm trying to understand why filesystem servers need proxy memory
> objects for io_map(). Unfortunately, I don't have time to read all the
> relevant code right now... After a quick glance, my guess is that the
> proxy objects are used so the same pager can be provided to several
> clients mapping the same file, but with different permissions?

Yes.  The underlying limitation is that double-paging is evil.

> But if several clients share a pager, doesn't that mean there is no way
> to shut down an individual client's mapping when the client closes the
> file?

Closing a file does not remove the mappings.  From glibc manual on mmap:

 "A new reference for the file specified by FILEDES is created, which
  is not removed by closing the file.

Thanks,
Marcus