linux-kernel - Re: [PATCH] Add file permission mode helpers

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Date:	Wed, 03 Aug 2016 08:49:26 -0700
From:	Joe Perches <joe@...ches.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Baole Ni <baolex.ni@...el.com>,
	Russell King - ARM Linux <linux@...linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	chuansheng.liu@...el.com
Subject: Re: [PATCH] Add file permission mode helpers

On Wed, 2016-08-03 at 10:11 +0200, Ingo Molnar wrote:
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> > [ So I answered similarly to another patch, but I'll just re-iterate
> > and change the subject line so that it stands out a bit from the
> > millions of actual patches ]
> > 
> > On Tue, Aug 2, 2016 at 1:42 PM, Pavel Machek <pavel@....cz> wrote:
> > > Everyone knows what 0644 is, but noone can read S_IRUSR | S_IWUSR |
> > > S_IRCRP | S_IROTH (*). Please don't do this.
> > Absolutely. It's *much* easier to parse and understand the octal
> > numbers, while the symbolic macro names are just random line noise and
> > hard as hell to understand. You really have to think about it.
> > 
> > So we should rather go the other way: convert existing bad symbolic
> > permission bit macro use to just use the octal numbers.
> In addition to that I'd love to have something even easier to read, a few common 
> variants of the permissions field of 'ls -l' pre-defined. I did some quick 
> grepping, and collected the main variants that are in use:
> 
> 		PERM_r________	0400
> 		PERM_r__r_____	0440
> 		PERM_r__r__r__	0444

[etc]

While the proposed PERM_ variants are easily read,
using a single style instead of 2+ incompatible
symbolic styles makes treewide misuse identification
via grep style tools easier.