linux-kernel - Re: [PATCH] Fix order_base

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Message-ID: <CA+55aFxEszjub9-MJD0irFs8y3hzGe3Ph=7RqWfkJ-0jKFtCeA@mail.gmail.com>
Date:	Wed, 14 Dec 2011 15:55:34 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Howells <dhowells@...hat.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	"Robert P. J. Day" <rpjday@...shcourse.ca>
Subject: Re: [PATCH] Fix order_base_2(0)

On Wed, Dec 14, 2011 at 3:40 AM, David Howells <dhowells@...hat.com> wrote:
> The order_base_2() function is either wrongly documented or wrongly
> implemented.  In the preceding comment, it says that:
>
>        ob2(0) = 0

Let's just remove that comment. That's just crazy math and makes no
sense. Why would anybody do ilog2() on zero and expect anything valid?

At least "-1" would make a tiny amount as sense as an error return or
"underflow" or whatever. But returning 0 is just wrong. That's
ilog2(1), not 0.

Does anybody actually *want* order_base_2(0)?

                      Linus
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