linux-kernel - Re: [PATCH] Fix get

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Message-ID: <45EDB82F.8030803@zytor.com>
Date:	Tue, 06 Mar 2007 10:51:27 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	David Howells <dhowells@...hat.com>
CC:	torvalds@...l.org, akpm@...l.org, benh@...nel.crashing.org,
	linux-kernel@...r.kernel.org, johannes@...solutions.net
Subject: Re: [PATCH] Fix get_order() [try #2]

David Howells wrote:
> H. Peter Anvin <hpa@...or.com> wrote:
> 
>> Why not just make it ((n) < 1 ? 0 : ...) and make it well-defined for
>> n == 0?
> 
> Because log2(0) is -INF or mathematically undefined or something isn't it?

Yes, but it's a *rounding up* function.  In this case, it makes sense to 
round up 0 to 1.  This is, in fact, a common way to handle requests for 
zero-byte allocation in order to be able to return a unique address for 
each one, so it's not a spurious thing.

	-hpa
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