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

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Message-ID: <20090616181325.GC23969@random.random>
Date:	Tue, 16 Jun 2009 20:13:26 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Izik Eidus <ieidus@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	nickpiggin@...oo.com.au
Subject: Re: running get_user_pages() from kernel thread

On Tue, Jun 16, 2009 at 09:05:27PM +0300, Izik Eidus wrote:
> So the question is: is this thing is by desgin? (that kernel thread cant 
> call get_user_pages???), should i use something like switch_mm()??

I think switch_mm trick should be used for page faults, but gup
shouldn't require it because it gets the 'mm' as parameter and the
current->mm has to be irrelevant. current->mm is only relevant for
gup-fast (obviously :). So I think the only bit that needs fixing is
grab_swap_token to not run if current->mm is null.
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