linux-kernel - RE: [PATCH 0/10] use safer test on the result of find_first_zero

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1725705F@AcuExch.aculab.com>
Date:	Wed, 4 Jun 2014 09:46:17 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Julia Lawall' <julia.lawall@...6.fr>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	linux-rdma <linux-rdma@...r.kernel.org>,
	"kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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	driverdevel <devel@...verdev.osuosl.org>,
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	scsi <linux-scsi@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	"adi-buildroot-devel@...ts.sourceforge.net" 
	<adi-buildroot-devel@...ts.sourceforge.net>
Subject: RE: [PATCH 0/10] use safer test on the result of find_first_zero_bit

From: Julia Lawall
> On Wed, 4 Jun 2014, Geert Uytterhoeven wrote:
> 
> > Hi Julia,
> >
> > On Wed, Jun 4, 2014 at 11:07 AM, Julia Lawall <Julia.Lawall@...6.fr> wrote:
> > > Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
> > > return a larger number than the maximum position argument if that position
> > > is not a multiple of BITS_PER_LONG.
> >
> > Shouldn't this be fixed in find_first_zero_bit() instead?
> 
> OK, I could do that as well.  Most of the callers currently test with >=.
> Should they be left as is, or changed to use ==?

Do we want to add an extra test to find_first_zero_bit() and effectively
slow down all the calls - especially those where the length is a
multiple of 8 (probably the most common).

Maybe the documented return code should be changed to allow for the
existing behaviour.

	David



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