linux-kernel - Re: [PATCH] mmc: vub300: Use common code in __download_offload

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Message-ID: <CAPDyKFp7zRLyGR4UfC8A3py8M9ZDi4nyeU8qUSg4NSrwSLh0HA@mail.gmail.com>
Date:   Tue, 31 Oct 2017 16:10:32 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     SF Markus Elfring <elfring@...rs.sourceforge.net>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        Tony Olech <tony.olech@...ndigitalsystems.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] mmc: vub300: Use common code in __download_offload_pseudocode()

On 31 October 2017 at 09:45, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> On Mon, Oct 30, 2017 at 02:03:13PM +0100, Ulf Hansson wrote:
>> On 30 October 2017 at 13:15, Dan Carpenter <dan.carpenter@...cle.com> wrote:
>> > On Mon, Oct 30, 2017 at 12:40:39PM +0100, Ulf Hansson wrote:
>> >> On 27 October 2017 at 21:31, SF Markus Elfring
>> >> <elfring@...rs.sourceforge.net> wrote:
>> >> > From: Markus Elfring <elfring@...rs.sourceforge.net>
>> >> > Date: Fri, 27 Oct 2017 21:21:40 +0200
>> >> >
>> >> > Add a jump target so that a specific string copy operation is stored
>> >> > only once at the end of this function implementation.
>> >> > Replace two calls of the function "strncpy" by goto statements.
>> >> >
>> >> > This issue was detected by using the Coccinelle software.
>> >> >
>> >> > Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
>> >>
>> >> Thanks, applied for next!
>> >>
>> >
>> > What's the advantage of this patch?  The new code seems more complicated
>> > to me and GCC automatically reuses duplicate constant strings so there
>> > is no memory savings.
>>
>> It looked to me that the error path got a bit cleaner. However, I
>> guess it's matter of taste.
>>
>> If you insist, I can drop it.
>
> I'm on the kernel-janitors list so I am CC'd on all of Markus's patches.
> It's not my code and I'm tired of being the anti-Markus guy so this
> patch is fine.  Markus has a tool that finds duplicate strings and he
> uses gotos to avoid them.  I don't think duplicate strings are a problem
> or that it's a good idea to send over a hundred patches using this
> method.  But many people have explained that to Markus already and
> that's not the bigger picture which is about error handling and labels.
>
> What I like are labels that are necessary and self explanatory.  Things
> like "goto unlock" are a good example, because we know we need to unlock
> and the goto tells us what the label does.  Or here is another example:
>
>         foo = alloc_foo();
>         if (!foo)
>                 return -ENOMEM;
>
>         bar = alloc_bar();
>         if (!foo) {
>                 err = -ENOMEM;
>                 goto free_foo;
>         }
>
> From reading the code, you know that you have to free foo and the label
> name is clear so you literally don't need to scroll down to the bottom
> of the function when you're reading this code.  A bad label is like
> this:
>
>         foo = alloc_foo();
>         if (!foo)
>                 goto err;
>
> You're reading along and you're like "what happens at the err" label?
> So then you have to scroll down to the bottom and read the code, then
> you have to think about how the variables line up with the variables
> in the above code, then you have to scroll back and find your place
> again and by that point you've forgotten what you were doing when you
> started.

Thanks for the details! Much appreciated!

Regarding posts from Markus' I am well aware of the problems.

In my case, it hasn't been much of a hurdle, I simply ignore changes
that seems silly to me.

Kind regards
Uffe