linux-kernel - Re: [PATCH 0/3] mm: rename confusing function names

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Message-Id: <20130205141332.04fcceac.akpm@linux-foundation.org>
Date:	Tue, 5 Feb 2013 14:13:32 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Zhang Yanfei <zhangyanfei.yes@...il.com>,
	Linux MM <linux-mm@...ck.org>, mgorman@...e.de,
	minchan@...nel.org, kamezawa.hiroyu@...fujitsu.com,
	m.szyprowski@...sung.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] mm: rename confusing function names

On Tue, 5 Feb 2013 14:26:40 -0500
Johannes Weiner <hannes@...xchg.org> wrote:

> On Wed, Feb 06, 2013 at 01:09:55AM +0800, Zhang Yanfei wrote:
> > Function nr_free_zone_pages, nr_free_buffer_pages and nr_free_pagecache_pages
> > are horribly badly named, they count present_pages - pages_high within zones
> > instead of free pages, so why not rename them to reasonable names, not cofusing
> > people.
> > 
> > patch2 and patch3 are based on patch1. So please apply patch1 first.
> > 
> > Zhang Yanfei (3):
> >   mm: rename nr_free_zone_pages to nr_free_zone_high_pages
> >   mm: rename nr_free_buffer_pages to nr_free_buffer_high_pages
> >   mm: rename nr_free_pagecache_pages to nr_free_pagecache_high_pages
> 
> I don't feel that this is an improvement.
> 
> As you said, the "free" is already misleading, because those pages
> might all be allocated.  "High" makes me think not just of highmem,
> but drug abuse in general.
> 
> nr_available_*_pages?  I don't know, but if we go through with all
> that churn, it had better improve something.

Yes, those names are ghastly.

Here's an idea: accurately document the functions with code comments. 
Once this is done, that documentation may well suggest a good name ;)


While we're there, please note that nr_free_buffer_pages() has a *lot*
of callers.  Generally it's code which is trying to work out what is an
appropriate size for preallocated caching space, lookup tables, etc. 

That's a rather hopeless objective, given memory hotplug, mlock, etc. 
But please do take a look at *why* these callers are calling
nr_free_buffer_pages() and let's ensure that both the implementation
and name are appropriate to their requirements.



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