Subject: Re: NFS structure allocation alignment patch
From: David Woodhouse <dwmw2@infradead.org>
To: Richard Curnow <Richard.Curnow@superh.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
       Marcelo Tosatti <marcelo@conectiva.com.br>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Paul Mundt <lethal@linux-sh.org>,
       Ben Gaster <Benedict.Gaster@superh.com>,
       Sean McGoogan <sean.mcgoogan@superh.com>,
       Boyd Moffat <boyd.moffat@superh.com>
In-Reply-To: <20030630135233.GN5586@malvern.uk.w2k.superh.com>
References: <20030630135233.GN5586@malvern.uk.w2k.superh.com>
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Date: Thu, 10 Jul 2003 12:05:21 +0100
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On Mon, 2003-06-30 at 14:52, Richard Curnow wrote:
> Hi Trond, Marcelo,
> 
> Below is a patch against 2.4.21 to tidy up the allocation of two
> structures in nfs3_proc_unlink_setup.  We need this change for NFS to
> work on the sh64 architecture, which has just been merged into 2.4 in
> the last couple of days.  Otherwise, 'res' is 4-byte aligned but not
> necessarily 8-byte aligned, but struct nfs_attr contains fields that are
> 8 bytes wide.  This leads to alignment exceptions on loads and stores
> into that structure.

What's wrong with alignment exceptions? They get fixed up by your
exception handler, surely?

If you assert that it's a performance-critical path and hence we
shouldn't be relying on the exception fixup, that's fine -- but in that
case it's not a correctness fix, it's just an optimisation.

-- 
dwmw2

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