Date: Wed, 30 Jul 2008 10:03:55 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Adrian Bunk <bunk@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>, lguest <lguest@ozlabs.org>,
       linux-kernel@vger.kernel.org, Nick Piggin <nickpiggin@yahoo.com.au>
Subject: Re: [PATCH 1/2] Export get_user_pages_fast
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	<20080730033523.0f38f7e4.akpm@linux-foundation.org>
	<20080730154736.GC21597@cs181140183.pp.htv.fi>
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On Wed, 30 Jul 2008 18:47:36 +0300 Adrian Bunk <bunk@kernel.org> wrote:

> On Wed, Jul 30, 2008 at 03:35:23AM -0700, Andrew Morton wrote:
> > On Wed, 30 Jul 2008 14:38:55 +1000 Rusty Russell <rusty@rustcorp.com.au> wrote:
> > 
> > > After all, it was made for lguest wasn't it?  Still think it should be
> > > called get_current_pages() though.
> > > 
> > > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> > > ---
> > >  arch/x86/mm/gup.c |    2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff -r cb465381f6d5 arch/x86/mm/gup.c
> > > --- a/arch/x86/mm/gup.c	Wed Jul 30 10:18:44 2008 +1000
> > > +++ b/arch/x86/mm/gup.c	Wed Jul 30 14:22:53 2008 +1000
> > > @@ -8,6 +8,7 @@
> > >  #include <linux/mm.h>
> > >  #include <linux/vmstat.h>
> > >  #include <linux/highmem.h>
> > > +#include <linux/module.h>
> > >  
> > >  #include <asm/pgtable.h>
> > >  
> > > @@ -296,3 +303,4 @@ slow_irqon:
> > >  		return ret;
> > >  	}
> > >  }
> > > +EXPORT_SYMBOL_GPL(get_user_pages_fast);
> > 
> > A regularly-occurring problem with an export like this is that someone
> > writes a driver and tests it on x86, then the driver explodes on an
> > architecture which didn't export the same symbol.
> > 
> > So a better implementation might be to put
> > 
> > #ifdef CONFIG_HAVE_GET_USER_PAGES_FAST
> > EXPORT_SYMBOL_GPL(get_user_pages_fast);
> > #endif
> > 
> > into generic code somewhere.
> 
> How would that help?
> 

It would fix the problem which I described.
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