linux-kernel - Re: [RFC][PATCH 02/10] mm: Remove likely() from mapping

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Message-ID: <1291964792.24978.3.camel@Joe-Laptop>
Date:	Thu, 09 Dec 2010 23:06:32 -0800
From:	Joe Perches <joe@...ches.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Rik van Riel <riel@...hat.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>
Subject: Re: [RFC][PATCH 02/10] mm: Remove likely() from
 mapping_unevictable()

On Fri, 2010-12-10 at 16:00 +0900, KOSAKI Motohiro wrote:
> > [ Resending to Nick's real email ]
> > 
> > 
> > From: Steven Rostedt <srostedt@...hat.com>
> > 
> > The mapping_unevictable() has a likely() around the mapping parameter.
> > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
[]
> >  static inline int mapping_unevictable(struct address_space *mapping)
> >  {
> > -	if (likely(mapping))
> > +	if (mapping)
> >  		return test_bit(AS_UNEVICTABLE, &mapping->flags);
> >  	return !!mapping;
> >  }
> I think you are right.
> 	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

It'd be better to use

	if (!mapping)
		return 0;
	return test_bit(AS_UNEVICTABLE, &mapping->flags);

to avoid the unnecessary !!

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