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

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Message-ID: <20110107190229.GX31708@n2100.arm.linux.org.uk>
Date:	Fri, 7 Jan 2011 19:02:29 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Marc Kleine-Budde <m.kleine-budde@...gutronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	Parisc List <linux-parisc@...r.kernel.org>,
	linux-arch@...r.kernel.org
Subject: Re: still nfs problems [Was: Linux 2.6.37-rc8]

On Fri, Jan 07, 2011 at 01:53:25PM -0500, Trond Myklebust wrote:
> I'd still like to keep the existing code for those architectures that
> don't have problems, since that allows us to send 32k READDIR requests
> instead of being limited to 4k. For large directories, that is a clear
> win.
> For the NOMMU case we will just go back to using a single page for
> storage (and 4k READDIR requests only). Should I just do the same for
> architectures like ARM and PARISC?

I think you said that readdir reads via the vmalloc mapping of the
group of pages, but XDR writes to the individual pages.

As I understand NFS, you receive a packet, you then have to use XDR
to unpack the data, which you presumably write into the set of
struct page *'s using kmap?

Isn't a solution to have XDR write directly into the vmalloc mapping
rather than using struct page * and kmap?
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