linux-kernel - Re: [PATCH] mm: Use octal not symbolic permissions

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Date:   Wed, 28 Mar 2018 08:44:51 -0700
From:   Joe Perches <joe@...ches.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: Use octal not symbolic permissions

On Wed, 2018-03-28 at 15:06 +0200, Michal Hocko wrote:
> On Mon 26-03-18 15:22:32, Joe Perches wrote:
> > mm/*.c files use symbolic and octal styles for permissions.
> > 
> > Using octal and not symbolic permissions is preferred by many as more
> > readable.
> > 
> > https://lkml.org/lkml/2016/8/2/1945
> > 
> > Prefer the direct use of octal for permissions.
> > 
> > Done using
> > $ scripts/checkpatch.pl -f --types=SYMBOLIC_PERMS --fix-inplace mm/*.c
> > and some typing.
> > 
> > Before:	 $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
> > 44
> > After:	 $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
> > 86
> 

> Ohh, I absolutely detest those symbolic names. I always have to check
> what they actually mean to be sure. Octal representation is quite
> natural to read. So for once I am really happy about such a clean up
> change.
> 
> Btw. something like this should be quite easy to automate via
> coccinelle AFAIU. 

checkpatch is currently better at this, for some
definition of better, than Coccinelle.

Julia and I had a discussion about it awhile ago.
https://lkml.org/lkml/2017/2/4/140

S_<FOO> groupings need to be combined and can
appear in arbitrary order.

Coccinelle would need the same octal addition in
some code path as checkpatch already has.

> > Miscellanea:
> > 
> > o Whitespace neatening around these conversions.
> > 
> > Signed-off-by: Joe Perches <joe@...ches.com>
> 
> I hope I haven't overlooked any potential mismatch...

Doubtful as the conversion is completely automated.