linux-kernel - Re: [Drbd-dev] [Patch] drbd: check MODULE for THIS

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Message-ID: <20120412083316.GK9163@barkeeper1-xen.linbit>
Date:	Thu, 12 Apr 2012 10:33:16 +0200
From:	Lars Ellenberg <lars.ellenberg@...bit.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Cong Wang <xiyou.wangcong@...il.com>, linux-kernel@...r.kernel.org,
	Lars Ellenberg <drbd-dev@...ts.linbit.com>
Subject: Re: [Drbd-dev] [Patch] drbd: check MODULE for THIS_MODULE

On Mon, Apr 09, 2012 at 04:14:27PM -0700, Andrew Morton wrote:
> On Tue,  3 Apr 2012 14:13:36 +0800
> Cong Wang <xiyou.wangcong@...il.com> wrote:
> 
> > THIS_MODULE is NULL only when drbd is compiled as built-in,
> > so the #ifdef CONFIG_MODULES should be #ifdef MODULE instead.
> > 
> > This fixes the warning:
> > 
> > drivers/block/drbd/drbd_main.c: In function ___drbd_buildtag___:
> > drivers/block/drbd/drbd_main.c:4187:24: warning: the comparison will always evaluate as ___true___ for the address of _____this_module___ will never be NULL [-Waddress]
> > 
> > Cc: Lars Ellenberg <drbd-dev@...ts.linbit.com>
> > Signed-off-by: WANG Cong <xiyou.wangcong@...il.com>
> > 
> > ---
> > diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
> > index 211fc44..96c432f 100644
> > --- a/drivers/block/drbd/drbd_main.c
> > +++ b/drivers/block/drbd/drbd_main.c
> > @@ -4183,12 +4183,11 @@ const char *drbd_buildtag(void)
> >  	static char buildtag[38] = "\0uilt-in";
> >  
> >  	if (buildtag[0] == 0) {
> > -#ifdef CONFIG_MODULES
> > -		if (THIS_MODULE != NULL)
> > -			sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
> > -		else
> > +#ifdef MODULE
> > +		sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
> > +#else
> > +		buildtag[0] = 'b';
> >  #endif
> > -			buildtag[0] = 'b';
> >  	}
> >  
> >  	return buildtag;
> 
> If the MODULE_SRCVERSION_ALL help in init/Kconfig is to be believed,
> this should depend on CONFIG_MODULE_SRCVERSION_ALL?
> 
> But drbd is the only driver in all of Linux which plays with
> srcversion.  Can we just delete this code?

Technically we sure can.

cat /proc/drbd is the first thing we ask for in problem reports, and it
sure helps and saves a few roundtrips knowing which exact version of
in-tree or out-of-tree drbd version is in use.
For an out-of-tree build, we print the exact git-hash there.
For an in-tree build, the srcversion was the "obvious" substitute.
If it is not too much trouble, I'd like to keep that info.

	Lars
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