From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: 2.4 vs 2.6
Date: Tue, 13 Jun 2006 16:42:25 -0400
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Cc: mehta kiran <kiranmehta1981@yahoo.com>,
	Vijay Chauhan <kernel.vijay@gmail.com>, nfs@lists.sourceforge.net,
	Greg Banks <gnb@sgi.com>
To: Neil Brown <neilb@suse.de>
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On Tue, Jun 13, 2006 at 01:29:42PM +1000, Neil Brown wrote:
> Having the mapping permanently in the kernel rather than filled in on
> demand would mean that:
> 
>  - the filesystem has to be mounted the whole time, and we cannot do
>    any on-demand mounting (based on fsid) - not that we currently do.
>    This is a fairly small point however.

Fair enough.

>    If a request arrives from a host which is in both 'somehosts' and
>    'otherhosts', then what name do you give to the kernel for that IP
>    address?
>    We currently say the IP address maps to 
>           @somehosts+@otherhosts
>    (or something like that) and then tell the kernel any of the
>    following as required:
>           /export1 @somehosts+@otherhosts  -> rw,root_squash
>           /export1 @somehosts  -> rw,root_squash
>           /export2 @somehosts+@otherhosts  -> ro,no_root_squash
>           /export2 @otherhosts  -> ro,no_root_squash

The kernel could of course just split these plus+separated+name+lists
itself before mapping to export options.  But I guess the point is that
in cases such as the above there's a policy decision that's better made
in userspace.  OK.

> Hopefully you can see that giving a full (path, client-name ) ->
> export mapping the kernel in advance is not practical.

Just to be clear--I'm definitely not on some crusade to change all this.
I'm just curious about the motivation for the design; thanks for the
explanation.

--b.


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