Re: [PATCH 11/13] nvdimm: Use more common logic testing styles and bare ; positions

From: "Verma, Vishal L" <vishal.l.verma@intel.com>
To: "joe@perches.com" <joe@perches.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	"Jiang, Dave" <dave.jiang@intel.com>,
	"Busch, Keith" <keith.busch@intel.com>,
	"Weiny, Ira" <ira.weiny@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dan.carpenter@oracle.com" <dan.carpenter@oracle.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH 11/13] nvdimm: Use more common logic testing styles and bare ; positions
Date: Thu, 12 Sep 2019 03:52:49 +0000	[thread overview]
Message-ID: <706f6af6a6571a3bb2d35ec332fa572a990cbc48.camel@intel.com> (raw)
In-Reply-To: <d6aa5b66936f2e0f132e893e10494aae6b74e886.1568256708.git.joe@perches.com>

On Wed, 2019-09-11 at 19:54 -0700, Joe Perches wrote:
> Avoid using uncommon logic testing styles to make the code a
> bit more like other kernel code.
> 
> e.g.:
> 	if (foo) {
> 		;
> 	} else {
> 		<code>
> 	}
> 
> is typically written
> 
> 	if (!foo) {
> 		<code>
> 	}
> 

A lot of times the excessive inversions seem to result in a net loss of
readability - e.g.:

<snip>

> diff --git a/drivers/nvdimm/region_devs.c
> b/drivers/nvdimm/region_devs.c
> index 65df07481909..6861e0997d21 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -320,9 +320,7 @@ static ssize_t set_cookie_show(struct device *dev,
>  	struct nd_interleave_set *nd_set = nd_region->nd_set;
>  	ssize_t rc = 0;
>  
> -	if (is_memory(dev) && nd_set)
> -		/* pass, should be precluded by region_visible */;

For one, the comment is lost

> -	else
> +	if (!(is_memory(dev) && nd_set))

And it takes a moment to resolve between things such as:

	if (!(A && B))
	  vs.
	if (!(A) && B)

And this is especially true if 'A' and 'B' are longer function calls,
split over multiple lines, or are themselves compound 'sections'.

I'm not opposed to /all/ such transformations -- for example, the ones
where the logical inversion can be 'consumed' by toggling a comparision
operator, as you have a few times in this patch, don't sacrifice any
readibility, and perhaps even improve it. 

>  		return -ENXIO;
>  
>  	/*
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