linux-kernel - Re: [GIT PULL] Please pull NFS client bugfixes....

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Date:	Thu, 07 Jan 2010 20:03:21 -0500
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] Please pull NFS client bugfixes....

On Thu, 2010-01-07 at 16:34 -0800, Linus Torvalds wrote: 
> 
> On Thu, 7 Jan 2010, Trond Myklebust wrote:
> > 
> > Yes. I want to pursue Peter Zijlstra's patches, which split up the mmap
> > function into a set of parts which require the mmap_sem, and other parts
> > which don't, and that adds a filesystem callback that allows for
> > revalidation to occur outside the mmap_sem.
> 
> I'm sorry, but that just sounds STUPID.
> 
> Why?
> 
> Because it means that you can trivially take page faults before the thing 
> is validated (think threads).

Which would mean that another process/thread already has part of the
file mmapped on the same client. I'm not arguing that have to revalidate
in _that_ case.

> If that is ok, then why do the revalidate at all? Just do the open/close 
> consistency and validate at open time, not mmap time.

That violates the expected semantics of the 'noac' mount option.

Trond
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