linux-kernel - Re: [PATCH -next] bcache: use DEFINE

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Date:   Thu, 29 Apr 2021 08:56:34 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Muhammad Usama Anjum <musamaanjum@...il.com>
Cc:     Coly Li <colyli@...e.de>, Zheng Yongjun <zhengyongjun3@...wei.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        linux-bcache@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Hulk Robot <hulkci@...wei.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] bcache: use DEFINE_MUTEX() for mutex lock

On Wed, Apr 28, 2021 at 09:19:26PM +0500, Muhammad Usama Anjum wrote:
> On Tue, 2021-04-06 at 02:17 +0500, Muhammad Usama Anjum wrote:
> > On Mon, 2021-04-05 at 22:02 +0800, Coly Li wrote:
> > > On 4/5/21 6:14 PM, Zheng Yongjun wrote:
> > > > mutex lock can be initialized automatically with DEFINE_MUTEX()
> > > > rather than explicitly calling mutex_init().
> > > > 
> > > > Reported-by: Hulk Robot <hulkci@...wei.com>
> > > > Signed-off-by: Zheng Yongjun <zhengyongjun3@...wei.com>
> > > 
> > > NACK. This is not the first time people try to "fix" this location...
> > > 
> > > Using DEFINE_MUTEX() does not gain anything for us, it will generate
> > > unnecessary extra size for the bcache.ko.
> > > ines.
> > 
> > How can the final binary have larger size by just static declaration?
> > By using DEFINE_MUTEX, the mutex is initialized at compile time. It'll
> > save initialization at run time and one line of code will be less also
> > from text section. 
> > 
> > #### with no change (dynamic initialization)
> > size drivers/md/bcache/bcache.ko
> >    text	   data	    bss	    dec	    hex	filename
> >  187792	  25310	    152	 213254	  34106	drivers/md/bcache/bcache.ko
> > 
> > #### with patch applied (static initialization)
> >    text	   data	    bss	    dec	    hex	filename
> >  187751	  25342	    120	 213213	  340dd	drivers/md/bcache/bcache.ko
> > 
> > Module's binary size has decreased by 41 bytes with the path applied
> > (x86_64 arch).
> > 
> Anybody has any thoughts on it?
>

I think you're right and the response is puzzling.  But who cares?  It's
a small thing.  Leave it and move on.

regards,
dan carpenter