linux-kernel - Re: [PATCH] Fix kunmap_atomic's use of kpte_clear

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Message-ID: <45512E9C.9030702@goop.org>
Date:	Tue, 07 Nov 2006 17:10:52 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Andrew Morton <akpm@...l.org>, Zachary Amsden <zach@...are.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix kunmap_atomic's use of kpte_clear_flush()

Rusty Russell wrote:
> On Tue, 2006-11-07 at 16:22 -0800, Jeremy Fitzhardinge wrote:
>   
>> kunmap_atomic() will call kpte_clear_flush with vaddr/ptep arguments
>> which don't correspond if the vaddr is just a normal lowmem address
>> (ie, not in the KMAP area).  This patch makes sure that the pte is
>> only cleared if kmap area was actually used for the mapping.
>>     
>
> Or in other words, if kmap_atomic() does nothing, kunmap_atomic() should
> do nothing.
>   

Sure.  I guess there's no particular reason why kmap_atomic() couldn't 
always map, but I guess avoid the pagetable updates is worthwhile.

    J
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