linux-kernel - Re: [RFCv5 3/9] mm: cma: Added SysFS support

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Date:	Tue, 07 Sep 2010 07:31:30 +0200
From:	Michał Nazarewicz <m.nazarewicz@...sung.com>
To:	Greg KH <greg@...ah.com>
Cc:	Hans Verkuil <hverkuil@...all.nl>,
	Peter Zijlstra <peterz@...radead.org>,
	Daniel Walker <dwalker@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Corbet <corbet@....net>, Mel Gorman <mel@....ul.ie>,
	Pawel Osciak <p.osciak@...sung.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-kernel@...r.kernel.org,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	linux-mm@...ck.org, Kyungmin Park <kyungmin.park@...sung.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Zach Pfeffer <zpfeffer@...eaurora.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [RFCv5 3/9] mm: cma: Added SysFS support

Hello Greg,

Thanks for reviewing the sysfs part.  Actually, I was never really sure
if I shouldn't rather put this code to debugfs and you got me convinced
that I should.  Sysfs somehow looked more appealing from kernel's API
point of view -- things seem to be more organised in sysfs than in
debugfs.  It seems I'll have to port it to debugfs after all

Nonetheless, a few responses to your comments:

> On Mon, Sep 06, 2010 at 08:33:53AM +0200, Michal Nazarewicz wrote:
>> +		The "allocators" file list all registered allocators.
>> +		Allocators with no name are listed as a single minus
>> +		sign.

On Mon, 06 Sep 2010 23:07:47 +0200, Greg KH <greg@...ah.com> wrote:
> So this returns more than one value?

Aren't thing like cpufreq governors listed in a single sysfs file?
I remember there was such a file somewhere.  Has that been made
deprecated? I cannot seem to find any information on that.

>> +		The "regions" directory list all reserved regions.
>
> Same here?

regions is actually a directory with subdirectories for each
region. ;)

>> +static ssize_t cma_sysfs_region_name_show(struct cma_region *reg, char *page)
>> +{
>> +	return reg->name ? snprintf(page, PAGE_SIZE, "%s\n", reg->name) : 0;
>> +}

> Is a name field ever really going to be bigger than a page?

I prefer being on the safe side -- I have no idea what user will provide
as region name so I assume as little as possible.  For numeric values you
are right that snprintf() is a bit paranoid, still I see no good reason
why not to use it.

-- 
Best regards,                                        _     _
| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
+----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--

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