linux-kernel - Re: [PATCH] module: clean up initialization of variable

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Message-ID: <alpine.DEB.1.10.0901052059390.16409@gandalf.stny.rr.com>
Date:	Mon, 5 Jan 2009 21:02:07 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
cc:	Sam Ravnborg <sam@...nborg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux <sparclinux@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] module: clean up initialization of variable


On Tue, 6 Jan 2009, Rusty Russell wrote:

> On Tuesday 06 January 2009 07:00:25 Steven Rostedt wrote:
> > This is sloppy initialization because it initializes, not only in an
> > if condition, but also as the second part of a complex conditional.
> > 
> > This patch makes the code a bit easier to read.
> ...
> >  	/* Suck in entire file: we'll want most of it. */
> >  	/* vmalloc barfs on "unusual" numbers.  Check here */
> > -	if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
> > +	if (len > 64 * 1024 * 1024)
> > +		return ERR_PTR(-ENOMEM);
> > +	hdr = vmalloc(len);
> > +	if (hdr == NULL)
> >  		return ERR_PTR(-ENOMEM);
> >  	if (copy_from_user(hdr, umod, len) != 0) {
> >  		err = -EFAULT;
> 
> This line is not accidental nor casually written: the two statements 
> are deliberately entwined.  It is a succint complaint against the 
> vagaries of vmalloc.
> 
> So this patch is a messup, not a cleanup.

It is not that much of a messup. I did not realize that the code was
a political protest against the horrors of vmalloc ;-)

> 
> But it's really upset me because it is lazy and timid: and too much 
> kernel code is becoming mired in such scars.  Instead of "how do I kill 
> this warning and get it in the merge window" you should be thinking "how 
> do I make the kernel better", and "I wonder if vmalloc still has this 
> problem"...
> 
> And I so look forward to the warm fuzzies I get when applying a real 
> cleanup patch.

Well, I'm not about to go solve the vmalloc issues (not today anyway). But 
I'll go and see if I can get the branch tracer macro to work on all 
versions of gcc.

Thanks,

-- Steve

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