Subject: Re: MNT_NOSHARE for non-exportable fs [was: Removing tmpfs' experimental
To: Julio M. Merino Vidal <>
From: Cary G. Gray <>
List: tech-kern
Date: 10/30/2006 11:56:14
On Mon, 30 Oct 2006, Julio M. Merino Vidal wrote:
> However, it'd be different if this noexport option was set by the file
> system driver itself (I think this is what others suggested and is
> what I had in mind a long time ago during the rototill).  This way,
> tmpfs (or any other file system that wanted to for whatever reason)
> could say "hey, I don't want to be exported", and then you could not
> export it in any way.

At the risk of repetition, let me argue that it what is at issue here is 
not a security issue, nor is it really about "export".  The question is 
whether a particular filesystem can provide the guarantees required by a 
particular application (said application being the NFS server).  It isn't 
a case of "want", but "can".

The NFS server code can not correctly export from tmpfs, because tmpfs 
does not make the required guarantee about persistence of file handles. 
What is needed here is a way that the NFS code can query whether an 
underlying filesystem meets its requirements.  But the vocabulary of that 
query doesn't involve the word "export".

 	Cary Gray