linux-kernel - Re: [Drbd-dev] [PATCH v2] drbd: change one-bit bitfield to be an unsigned int

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Message-ID: <20140617105348.GH28884@soda.linbit>
Date:	Tue, 17 Jun 2014 12:53:48 +0200
From:	Lars Ellenberg <lars.ellenberg@...bit.com>
To:	Martin Kepplinger <martink@...teo.de>
Cc:	rientjes@...gle.com, linux-kernel@...r.kernel.org,
	drbd-dev@...ts.linbit.com
Subject: Re: [Drbd-dev] [PATCH v2] drbd: change one-bit bitfield to be an
 unsigned int

On Tue, Jun 17, 2014 at 08:54:07AM +0200, Martin Kepplinger wrote:
> The one-bit bitfields are assigned true (1) or false (0) and checked
> for them respectively. While it should work either way and -1 is true
> as well it is more clear to see what's going on when using an unsigned int
> because 1 doesn't silently become -1 behind the label true.
> 
> Signed-off-by: Martin Kepplinger <martink@...teo.de>
> ---
> Thanks for looking at it. This is more of a question: Does this make sense
> to you now? I can be mistaken. It just wasn't totally clear to me at first
> sight and even though it should be, why not try to improve it.
> 
> sparse called it 'dubious' before the change.
> 
> (built but untested)

Patch is completely pointless, really,
and I don't get the motivation for it at all.
BUT.

If it makes someone happy,
and since all of our other bitfields in fact are declared "unsigned xyz:N",
for consistency we can make this unsigned as well.
Will probably fold this with some upcoming change in that struct anyways.

    Lars

> 
>  drivers/block/drbd/drbd_interval.h |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
> index f38fcb0..8d670e6 100644
> --- a/drivers/block/drbd/drbd_interval.h
> +++ b/drivers/block/drbd/drbd_interval.h
> @@ -9,8 +9,8 @@ struct drbd_interval {
>  	sector_t sector;	/* start sector of the interval */
>  	unsigned int size;	/* size in bytes */
>  	sector_t end;		/* highest interval end in subtree */
> -	int local:1		/* local or remote request? */;
> -	int waiting:1;
> +	unsigned int local:1;	/* local or remote request? */
> +	unsigned int waiting:1;
>  };
>  
>  static inline void drbd_clear_interval(struct drbd_interval *i)
--
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