linux-kernel - Re: [PATCH] pagewalk: don't pte_unmap(NULL) in walk_pte

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Message-ID: <jer6dd9ajn.fsf@sykes.suse.de>
Date:	Thu, 10 Apr 2008 14:09:00 +0200
From:	Andreas Schwab <schwab@...e.de>
To:	Johannes Weiner <hannes@...urebad.de>
Cc:	Roel Kluin <12o3l@...cali.nl>, linux-mm@...ck.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pagewalk: don't pte_unmap(NULL) in walk_pte_range()

Johannes Weiner <hannes@...urebad.de> writes:

>> Signed-off-by: Roel Kluin <12o3l@...cali.nl>
>> ---
>> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
>> index 1cf1417..6615f0b 100644
>> --- a/mm/pagewalk.c
>> +++ b/mm/pagewalk.c
>> @@ -15,7 +15,7 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>>  		       break;
>>  	} while (pte++, addr += PAGE_SIZE, addr != end);
>>  
>> -	pte_unmap(pte);
>> +	pte_unmap(pte - 1);
>>  	return err;
>>  }
>
> This does not make any sense to me.

There is something fishy here.  If the loop ends because addr == end
then pte has been incremented past the pmd page for addr, no?

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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