linux-kernel - Re: [PATCH RESUBMIT 0/2] fs/seq_file: Add seq_open

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Date:	Thu, 25 Sep 2014 18:36:22 +0100
From:	Rob Jones <rob.jones@...ethink.co.uk>
To:	Kees Cook <keescook@...omium.org>
CC:	Randy Dunlap <rdunlap@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-kernel@...ethink.co.uk,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [PATCH RESUBMIT 0/2] fs/seq_file: Add seq_open_init()



On 25/09/14 17:09, Kees Cook wrote:
> On Thu, Sep 25, 2014 at 1:57 AM, Rob Jones <rob.jones@...ethink.co.uk> wrote:
>>
>>
>> On 24/09/14 19:06, Kees Cook wrote:
>>>
>>> On Wed, Sep 24, 2014 at 4:15 AM, Rob Jones <rob.jones@...ethink.co.uk>
>>> wrote:
>>>>
>>>> Series resubmitted due to a typo in an email address.
>>>>
>>>> This patch series implements and documents a new interface function for
>>>> seq_file.
>>>>
>>>> The existing set of open functions: seq_open(), seq_open_private() and
>>>> __seq_open_private() satisfy the majority of use cases however there is
>>>> one more use case that is also very common that this new function
>>>> addresses.
>>>>
>>>> This case is where the iterator needs information that is available only
>>>> at
>>>> the time the seq_file is opened but does not need any space allocated,
>>>> e.g.
>>>> access to the inode structure. This type of open occurs, by my best
>>>> estimate,
>>>> in well over 40 places.
>>>>
>>>> Using the new function saves at least two lines of boilerplate code per
>>>> instance as well as making the code easier to follow. The additional code
>>>> in seq_file.c to implement the function is minimal as the first place
>>>> that
>>>> code can be removed is within seq_file.c itself.
>>>>
>>>> Once this patch is accepted, the instances of boilerplate code can be
>>>> addressed.
>>>
>>>
>>> Would it be possible to write a coccinelle patch for the replacements?
>>
>>
>> I'm afraid I don't know what that means.
>
> It's a very flexible tool that should be able to find all the places
> where this pattern is being used, and you can replace it with the new
> function call:
>
> http://lwn.net/Articles/315686/

I suspect that the learning curve would exceed the utility but I'll have
a look at it. Unless there's a coccinelle expert available to do it, in
which case I could point them in the right direction.

My gut reaction would be that by the time I had analysed enough cases
to come up with a viable set of SmPL scripts I would have done most of
the work required, especially if I had to learn a new syntax and tool
to do it.

But first impressions aren't always right.

>
> -Kees
>
>

-- 
Rob Jones
Codethink Ltd
mailto:rob.jones@...ethink.co.uk
tel:+44 161 236 5575
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