linux-kernel - Re: running get_user_pages() from kernel thread

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Message-ID: <4A380BA1.4020106@redhat.com>
Date:	Tue, 16 Jun 2009 17:16:17 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Izik Eidus <ieidus@...hat.com>, linux-kernel@...r.kernel.org,
	nickpiggin@...oo.com.au
Subject: Re: running get_user_pages() from kernel thread

Johannes Weiner wrote:
> On Tue, Jun 16, 2009 at 07:38:39PM +0100, Hugh Dickins wrote:

>> --- 2.6.30-mm1/mm/thrash.c	2007-07-09 00:32:17.000000000 +0100
>> +++ linux/mm/thrash.c	2009-06-15 19:44:53.000000000 +0100
>> @@ -30,6 +30,9 @@ void grab_swap_token(void)
>>  {
>>  	int current_interval;
>>  
>> +	if (!current->mm)	/* kthread doing get_user_pages on an mm */
>> +		return;
>> +
> 
> Did you have a particular reason not to pass in the faulting mm
> instead?

If the task itself is not swapping, should we really give
it the swap token?

I admit, this could be a pretty weak reason :)

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