linux-kernel - Re: [RFC PATCH 2/2] treewide, bits: use ffs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aWFivp6fVa0vUFbo@yury>
Date: Fri, 9 Jan 2026 15:19:10 -0500
From: Yury Norov <ynorov@...dia.com>
To: Petr Tesarik <ptesarik@...e.com>
Cc: Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Richard Henderson <richard.henderson@...aro.org>,
	Matt Turner <mattst88@...il.com>,
	Magnus Lindholm <linmag7@...il.com>,
	Vineet Gupta <vgupta@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"Maciej W. Rozycki" <macro@...am.me.uk>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Chris Zankel <chris@...kel.net>, Max Filippov <jcmvbkbc@...il.com>,
	Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Oliver Neukum <oliver@...kum.org>, Arnd Bergmann <arnd@...db.de>,
	Kuan-Wei Chiu <visitorckw@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marcel Holtmann <marcel@...tmann.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Florian Westphal <fw@...len.de>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] treewide, bits: use ffs_val() where it is
 open-coded

On Fri, Jan 09, 2026 at 08:32:50PM +0100, Petr Tesarik wrote:
> On Fri, 9 Jan 2026 13:19:25 -0500
> Yury Norov <ynorov@...dia.com> wrote:
> 
> >[...]
> > --
> > 
> > OK, let me stop here.
> > 
> > Can you please instead of mechanical rework check each case
> > individually and find the best replacement to highlight the intention?
> > 
> > Can you also split this patch to a series according to subsystems, so
> > that corresponding maintainers will have better access to their changes?
> 
> Well, then it makes more sense to start by identifying the intention in
> every place and getting them fixed one by one. Whatever remains should
> be converted to use the new macro.
> 
> In fact, I can do both in parallel, converting the places where the
> result of ffs() is immediately used as a shift count.
> 
> Then no tree-wide change is necessary, as long as we can first get the
> helper (under whichever name) into bitops.h. But it will be rejected
> without an in-tree user. I somehow feel caught by Catch XXII.
> 
> Advice welcome. Non-ironically.

Build your series like this:

1. Switch all 'a & -a' chunks to the existing helpers where possible;
2. Introduce the new macro;
3. Convert the rest of the codebase to using the macro;

In cover-letter mention that patches from #1 may be taken individually
or together with the rest of the series at maintainers' discretion, and
#2 and 3 must be merged at once, for example with my branch.

Then depending on feedback, I'll take your series as is, or will take
only explicitly acked patches. In 2nd case, I will ask you to resend
non-acked part for better visibility, and then decide either take it
or drop.

Thanks,
Yury