Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver

Jens Axboe
2007-07-16T14:39:45Z

On Mon, Jul 16 2007, James Bottomley wrote:
> On Mon, 2007-07-16 at 14:16 +0200, 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.
>
> No ... that was the point of flush_kernel_dcache_page(). The page in
> question is page cache backed and contains user mappings. However, the
> block layer has already done a flush_dcache_page() in get_user_pages()
> and the user shouldn't be touching memory under I/O (unless they want
> self induced aliasing problems) so we're free to assume all the user
> cachelines are purged, hence all we have to do is flush the kernel alias
> to bring the page up to date and make the users see it correctly.

Oh indeed, I missed the flush_dcache_page() in get_user_pages().

--
Jens Axboe