From: glommer@br.ibm.com (Glauber de Oliveira Costa)
Subject: Re: [PATCH] Null pointer dereference at free_vm_area()
Date: Tue, 27 Dec 2005 14:17:23 -0200
Message-ID: <20051227161723.GB14912@br.ibm.com>
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	<20051227155449.GB4126@snarc.org>
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To: Vincent Hanquez <vincent.hanquez@cl.cam.ac.uk>
Cc: xen-devel@lists.xensource.com

> 
> Hi,
> 
> I quickly look around where free_vm_area is called, and I cannot see any
> codepath that could benefit such a code cleanup nor find any that
> could lead to a NULL pointer pass to it.
> 
> I think you should provide a use for this patch if you want it to be
> applied.
> 
> Thanks,
> -- 
> Vincent Hanquez
> 
I think it's more stylish than functional nowadays. In a situations in which we 
call alloc_vm_area() more than once, and test for the return value of them all 
in one shot. It can maybe lead to a cleaner code, as shown in the
pseudocode bellow. 

a1 = alloc_vm_area()
a2 = alloc_vm_area()

if (!a1 || !a2){
	free_vm_area(a1);
	free_vm_area(a2);
	return;
}

Instead of:

a1 = alloc_vm_area();
if (!a1)
	return;
a2 = alloc_vm_area()
if (!a2){
	free_vm_area(a1);
	return;
}

But of course, it's mainly a matter of opinion.

-- 
glommer