linux-kernel - Re: [RFC][PATCH] fs: configfs: programmatically create config groups

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Date:	Mon, 26 Nov 2012 17:56:04 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Andrzej Pietrasiewicz <andrzej.p@...sung.com>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Joel Becker <jlbec@...lplan.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [RFC][PATCH] fs: configfs: programmatically create config groups

> On 11/26/2012 09:35 AM, Andrzej Pietrasiewicz wrote:
>> In some parts of the kernel (e.g. planned configfs integration into usb
>> gadget) there is a need to programmatically create config groups
>> (directories) but it would be preferable to disallow creating them by
>> the user. This is more or less what default_groups used to be for.
>> But e.g. in the mass storage gadget, after storing the number of
>> luns (logical units) into some configfs attribute, the corresponding lun#
>> directories should be created, their number is not known up front so
>> default_groups are no good for this.
>>
>> Example:
>>
>> $ echo 3>  /cfg/..../mass_storage/luns
>>
>> causes
>>
>> /cfg/....../mass_storage/lun0
>> /cfg/....../mass_storage/lun1
>> /cfg/....../mass_storage/lun2

On Mon, Nov 26 2012, Sebastian Andrzej Siewior wrote:
> I though we did not want the luns file but instead use
>
> mkdir /cfg/....../mass_storage/lun0
> mkdir /cfg/....../mass_storage/lun1
>
> directly.

I think that's suboptimal, and we can do better.  There are too many
corner cases (ie. what if user does “mkdir lun7” without the previous
luns?), it adds complexity to the kernel (ie. parsing of the name), and
the thing is overly complicated for user (“echo 5 > nluns” is much nicer
than having to create 5 directories).

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--

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