linux-kernel - Re: BUG? linux-mips flush_dcache

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Message-ID: <20091016092418.GA3686@linux-mips.org>
Date:	Fri, 16 Oct 2009 11:24:18 +0200
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Atsushi Nemoto <anemo@....ocn.ne.jp>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-mips <linux-mips@...ux-mips.org>,
	Chungki woo <chungki.woo@...il.com>
Subject: Re: BUG? linux-mips flush_dcache_page

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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