linux-kernel - Re: [PATCH V2 mmots] fs/hfsplus/wrapper.c: replace shift loop by fls

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Message-Id: <20140519164037.ec6438686bd29efeebffa610@linux-foundation.org>
Date:	Mon, 19 May 2014 16:40:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Fabian Frederick <fabf@...net.be>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 mmots] fs/hfsplus/wrapper.c: replace shift loop by
 fls

On Mon, 19 May 2014 16:22:28 -0700 Joe Perches <joe@...ches.com> wrote:

> On Mon, 2014-05-19 at 16:09 -0700, Andrew Morton wrote:
> > On Fri, 16 May 2014 22:38:15 +0200 Fabian Frederick <fabf@...net.be> wrote:
> > > Replace while blocksize;shift by fls -1
> []
> > fls() always makes my brain hurt.  ilog() is nicer?
> 
> Maybe take an aspirin?
> 
> ilog2(n) is effectively fls(n) - 1

Precisely.  ilog2() means "integer log 2".  Whereas fls() is some weird
low-level bit-scanning thing.

What we want at this callsite is "integer log 2".  So use it.
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