From: Ian Kent <raven@themaw.net>
Subject: Re: [PATCH 1/2] NFS: Add the mount option "nosharecache"
Date: Fri, 18 May 2007 11:12:26 +0800
Message-ID: <1179457946.3726.3.camel@raven.themaw.net>
References: <17994.32412.173039.15055@notabene.brown>
	<20070517021318.32447.94991.stgit@heimdal.trondhjem.org>
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Cc: Neil Brown <neilb@suse.de>, Paul Krizak <paul.krizak@amd.com>,
	nfs@lists.sourceforge.net
To: Trond Myklebust <Trond.Myklebust@netapp.com>
In-Reply-To: <20070517021318.32447.94991.stgit@heimdal.trondhjem.org>
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On Wed, 2007-05-16 at 22:13 -0400, Trond Myklebust wrote:
> From: Trond Myklebust <Trond.Myklebust@netapp.com>
> 
> Prior to David Howell's mount changes in 2.6.18, users who mounted
> different directories which happened to be from the same filesystem on the
> server would get different super blocks, and hence could choose different
> mount options. As long as there were no hard linked files that crossed from
> one subtree to another, this was quite safe.
> Post the changes, if the two directories are on the same filesystem (have
> the same 'fsid'), they will share the same super block, and hence the same
> mount options.
> 
> Add a flag to allow users to elect not to share the NFS super block with
> another mount point, even if the fsids are the same. This will allow
> users to set different mount options for the two different super blocks, as
> was previously possible. It is still up to the user to ensure that there
> are no cache coherency issues when doing this, however the default
> behaviour will be to share super blocks whenever two paths result in
> the same fsid.
> 
> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

This looks great, thanks Trond.

I've been wondering about a couple things.

How will the "read-only bind mounts" VFS changes affect this?
When the fscache patches are merged how will this it be affect by this?

Comments please?

Ian


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