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Re: BUG? linux-mips flush_dcache_page

To: Minchan Kim <minchan.kim@gmail.com>
Subject: Re: BUG? linux-mips flush_dcache_page
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 16 Oct 2009 11:24:18 +0200
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>, lkml <linux-kernel@vger.kernel.org>, linux-mips <linux-mips@linux-mips.org>, Chungki woo <chungki.woo@gmail.com>
In-reply-to: <20091016141719.de606482.minchan.kim@barrios-desktop>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20091016141719.de606482.minchan.kim@barrios-desktop>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.19 (2009-01-05)
On Fri, Oct 16, 2009 at 02:17:19PM +0900, Minchan Kim wrote:

> Many code of kernel fs usually allocate high page and flush.
> But flush_dcache_page of mips checks PageHighMem to avoid flush
> so that data consistency is broken, I think. 

What processor and cache configuration?

> I found it's by you and Atsushi-san on 585fa724. 
> Why do we need the check?
> Could you elaborte please? 

The if statement exists because __flush_dcache_page would crash if a page
is not mapped.  This of course isn't correct but that wasn't a problem
since highmem still is only supported on machines that don't have aliases.

  Ralf

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