From: Trond Myklebust <Trond.Myklebust@netapp.com>
Subject: Re: inconsistent mount attributes (ro/rw), RHEL5 / Netapp
Date: Mon, 14 May 2007 19:11:59 -0400
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Cc: Paul Krizak <paul.krizak@amd.com>, nfs@lists.sourceforge.net,
	Ian Kent <raven@themaw.net>
To: Neil Brown <neilb@suse.de>
In-Reply-To: <17992.58783.827023.697258@notabene.brown>
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On Tue, 2007-05-15 at 08:41 +1000, Neil Brown wrote:
> I think "shared" is an important concept to have in there as it is
> sharing the cache, the connection and the options.  For consistency
> with other options, I would have an optional "no" at the front to
> invert the flag.  Current nfs options don't have punctuation, so I
> would probably go for something like:
>        -o  [no]sharedcache
>        -o  [no]shareconnection 
> 
> Then comes the question of what the default should be.
> The original default was nosharedcache, but the more recent default
> has been sharedcache.   In hindsight it would have been better not to
> change the default, but things are always much clearer in hindsight.
> 
> I would lean towards restoring the default to nosharedcache, and
> having to explicitly request sharedcache if you want that, and are
> happy to have the same mount option enforced on all sharing mounts.

I disagree with that. The default was changed for a very good reason,
namely that people were making assumptions that were wrong: i.e. that
the cache remains consistent when you change the ro/rw flag or try to
mount a subdirectory.
In fact, if you mounted the _same_ directory twice, then the default was
always 'sharedcache'.

So all we did in 2.6.18, was to make a consistent set of rules for how
this works.

The default should therefore remain 'sharedcache', preferably returning
an error if the user tries to mix metaphors.

Cheers
  Trond

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