linux-kernel - Re: still nfs problems [Was: Linux 2.6.37-rc8]

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Message-ID: <20110105190734.GI8638@n2100.arm.linux.org.uk>
Date:	Wed, 5 Jan 2011 19:07:34 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Marc Kleine-Budde <mkl@...gutronix.de>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, linux-nfs@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Marc Kleine-Budde <m.kleine-budde@...gutronix.de>
Subject: Re: still nfs problems [Was: Linux 2.6.37-rc8]

On Wed, Jan 05, 2011 at 01:55:05PM -0500, Trond Myklebust wrote:
> On Wed, 2011-01-05 at 18:27 +0000, Russell King - ARM Linux wrote: 
> > I do still think you need _something_ there, otherwise data can remain
> > in the direct map alias and not be visible via the vmap alias.  I don't
> > see that we have anything in place to handle this at present though.
> 
> Is that perhaps what flush_kernel_dcache_page() is supposed to do?

Well, given how we have things currently setup on ARM, this ends up
being a no-op - as new page cache pages are marked dirty and their
flushing done at the point when they're mapped into userspace.

I guess we could do the flushing there and mark the page clean, but
it'd need some careful examination of various code paths to confirm
that it's safe - we may be avoiding this because some ARM arch
versions need to manually IPI cache flushes to other cores (which
can only be done with IRQs enabled.)

So, I don't think it'll do at the present time.
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