linux-ext4 - Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

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Message-ID: <1279825160.3621.71.camel@heimdal.trondhjem.org>
Date:	Thu, 22 Jul 2010 14:59:20 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Volker.Lendecke@...Net.DE
Cc:	Jeremy Allison <jra@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Jan Engelhardt <jengelh@...ozas.de>,
	linux-cifs@...r.kernel.org, linux-nfs@...r.kernel.org,
	samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make
 extended  file stats available [ver #6]

On Thu, 2010-07-22 at 20:04 +0200, Volker Lendecke wrote:
> On Thu, Jul 22, 2010 at 11:02:04AM -0700, Jeremy Allison wrote:
> > On Thu, Jul 22, 2010 at 12:58:50PM -0400, Trond Myklebust wrote:
> > > 
> > > That would make it impossible to export the filesystem with NFSv2 and
> > > v3. They do rely on ctime checking for certain operations (e.g. deciding
> > > when to invalidate access and acl caches). NFSv4 needs this too if the
> > > filesystem has no dedicated change attribute.
> > > 
> > > Still, I suppose the market for exporting the same filesystem with both
> > > NFS and Samba is limited...
> > 
> > Ask NetApp about that :-). They have built a rather large
> > business on just that fact :-).
> 
> Jeremy, how many hours have you spent getting "posix
> locking" to the point where it is now? :-)
> 
> Volker
> 
> P.S: For those not aware, "posix locking = yes" is
> cross-protocol byte range locking done by smbd to co-operate
> with local processes and NFS.

I said "limited", not "non-existent".

The fact remains that most of us would be hard pressed to name an
application that requires you to share the same dataset to both
Windows/CIFS and posix NFS clients. Everything from ACL models through
caseless vs case-aware filesystems and Windows vs posix locking
semantics tends to discourage mixing the two environments.

   Trond

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