linux-kernel - Re: [RFC PATCH 1/1] cleanup: use bool as return type for rwsem_is

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Message-ID: <20140607234411.GA9508@dastard>
Date:	Sun, 8 Jun 2014 09:44:11 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Pranith Kumar <bobby.prani@...il.com>,
	Pranith Kumar <pranith@...ech.edu>, peterz@...radead.org,
	linux-kernel@...r.kernel.org, tim.c.chen@...ux.intel.com,
	davidlohr@...com, mingo@...hat.com, xfs@....sgi.com
Subject: Re: [RFC PATCH 1/1] cleanup: use bool as return type for
 rwsem_is_locked

On Fri, Jun 06, 2014 at 07:39:30PM -0700, Joe Perches wrote:
> On Fri, 2014-06-06 at 21:41 -0400, Pranith Kumar wrote:
> > On 06/06/2014 08:59 PM, Pranith Kumar wrote:
> > > On 06/06/2014 08:18 PM, Dave Chinner wrote:
> > >> If you are going to change the return type to bool, then you should
> > >> also remove the manual "!!" conversions to a boolean return and let
> > >> the compiler do it in the most optimal way.
> > > Agreed, please find patch below:
> > Simplify the "!!" condition. This is much simpler. :)
> []
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> 
> > @@ -285,25 +285,25 @@ xfs_ilock_demote(
> >  }
> >  
> >  #if defined(DEBUG) || defined(XFS_WARN)
> > -int
> > +bool
> >  xfs_isilocked(
> >  	xfs_inode_t		*ip,
> >  	uint			lock_flags)
> >  {
> >  	if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) {
> >  		if (!(lock_flags & XFS_ILOCK_SHARED))
> > -			return !!ip->i_lock.mr_writer;
> > +			return (ip->i_lock.mr_writer != 0);
> 
> simpler still would be just removing the !! completely.
> I presume in no case would it make an actual difference
> in emitted code.
> 
> ie:
> 			return ip->i_lock.mr_writer;

Yup, that's exactly what I meant. Casting to a bool type does all
the work of squashing all non-zero values to 1...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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