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Message-ID: <20070716133316.GU5195@kernel.dk>
Date: Mon, 16 Jul 2007 15:33:17 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
Cc: James Bottomley <James.Bottomley@...elEye.com>,
Arnd Bergmann <arnd@...db.de>, linux-scsi@...r.kernel.org,
Linux Kernel Development <linux-kernel@...r.kernel.org>,
Alessandro Rubini <rubini@...ion.unipv.it>,
Linux/PPC Development <linuxppc-dev@...abs.org>,
Paul Mackerras <paulus@...ba.org>
Subject: Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver
On Mon, Jul 16 2007, Geert Uytterhoeven wrote:
> On Mon, 16 Jul 2007, Geert Uytterhoeven wrote:
> > On Mon, 16 Jul 2007, Jens Axboe wrote:
> > > On Mon, Jul 16 2007, Geert Uytterhoeven wrote:
> > > > On Fri, 13 Jul 2007, Geert Uytterhoeven wrote:
> > > > > Ah, that explains it. flush_dcache_page() is used in some drivers.
> > > > > I'll update my patches. Thanks for the comments!
> > > >
> > > > Does this look OK?
> > > > - Replaced KM_USER0 by KM_IRQ0 (all routines are either called from an
> > > > interrupt handler, from .request_fn (ps3disk), or from .queuecommand
> > > > (ps3rom))
> > >
> > > That looks good.
> > >
> > > > - Add a call to flush_kernel_dcache_page() in routines that write to buffers
> > >
> > > Hmm, I would have thought a flush_dcache_page() would be more
> > > appropriate, the backing could be page cache pages.
> >
> > OK, I'll change it to flush_dcache_page().
>
> Upon closer look, while flush_kernel_dcache_page() is a no-op on ppc64,
> flush_dcache_page() isn't. So I'd prefer to not call it if not really needed.
>
> And according to James, flush_kernel_dcache_page() should be sufficient...
>
> So I'm getting puzzled again...
I'll let James expand on why he thinks flush_kernel_dcache_page() should
be sufficient. If the backing is always user memory from
get_user_pages(), then the flush_kernel_dcache_page() looks sufficient.
For the normal IO paths, it could be that or page cache pages too for
instance.
--
Jens Axboe
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