From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AC36C433DB for ; Mon, 18 Jan 2021 13:54:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 572DE22B49 for ; Mon, 18 Jan 2021 13:54:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392563AbhARNyE (ORCPT ); Mon, 18 Jan 2021 08:54:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:39236 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392390AbhARNwp (ORCPT ); Mon, 18 Jan 2021 08:52:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5C3C622BF3; Mon, 18 Jan 2021 13:52:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610977924; bh=RYKwUEhOYF+48ucbpQAiFSGTxXhf8P32ggTSMqvERec=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mx6SA2wUZRNsiN7wGN5eUAQBhO7QcdYKOcrs+l5P23ZjC6GwsMOIWeq2IvH5l5foH uPwLKDKnMSIXdLMfCZDGUhqs38PaXBSQVNagAFlOHuEXF6dvwab1uIbpg1GgsufSQc coiLAsXiwjfZ+L6j/k7Wr24c1wDVpyFAH71sNerc= Date: Mon, 18 Jan 2021 14:52:02 +0100 From: Greg KH To: Sasha Levin Cc: masahiroy@kernel.org, michal.lkml@markovi.net, torvalds@linux-foundation.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: [PATCH] kbuild: give SUBLEVEL more room in KERNEL_VERSION Message-ID: References: <20210118014951.250815-1-sashal@kernel.org> <20210118133959.GZ4035784@sasha-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210118133959.GZ4035784@sasha-vm> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 18, 2021 at 08:39:59AM -0500, Sasha Levin wrote: > On Mon, Jan 18, 2021 at 10:24:33AM +0100, Greg KH wrote: > > On Mon, Jan 18, 2021 at 10:21:16AM +0100, Greg KH wrote: > > > On Sun, Jan 17, 2021 at 08:49:51PM -0500, Sasha Levin wrote: > > > > SUBLEVEL only has 8 bits of space, which means that we'll overflow it > > > > once it reaches 256. > > > > > > > > Few of the stable branches will imminently overflow SUBLEVEL while > > > > there's no risk of overflowing VERSION. > > > > > > > > Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this > > > > should create a better balance between the different version numbers we > > > > use. > > > > > > > > The downside here is that Linus will have 8 bits less to play with, but > > > > given our current release cadence (~10 weeks), the number of Linus's > > > > fingers & toes (20), and the current VERSION (5) we can calculate that > > > > VERSION will overflow in just over 1,000 years, so I'm kicking this can > > > > down the road. > > > > > > > > Cc: stable@kernel.org > > > > Signed-off-by: Sasha Levin > > > > --- > > > > Makefile | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/Makefile b/Makefile > > > > index 9e73f82e0d863..dc2bad7a440d8 100644 > > > > --- a/Makefile > > > > +++ b/Makefile > > > > @@ -1252,8 +1252,8 @@ endef > > > > > > > > define filechk_version.h > > > > echo \#define LINUX_VERSION_CODE $(shell \ > > > > - expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \ > > > > - echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' > > > > + expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \ > > > > + echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))' > > > > > > As much as I agree, this will break in-tree users of LINUX_VERSION_CODE > > > that try to suck out the version/patchlevel number of the kernel release > > > into their own fields. Things like USB host controller strings, v4l > > > ioctl reports, scsi driver ioctls, and other places do fun bit-movements > > > to try to unreverse this bit packing. > > > > > > So how about we just provide a "real" version/subversion/revision > > > #define as well, and clean up all in-kernel users, so we can get this to > > > work, and we can change it in the future more easily. > > > > Or, I can just stop doing stable releases at .255 and then abuse the > > EXTRAVERSION field to put in sub-revision values. > > > > Or, we can just not worry about it as anyone using these really old > > kernels, userspace will work just fine (the number going backwards for > > these fields isn't going to break anything), it's only any crazy > > out-of-tree code that will get confused if they are trying to do > > different build options based on SUBLEVEL :) > > I think it would also affect code that doesn't do things based on > SBULEVEL. Consider something like: > > if (LINUX_VERSION_CODE < KERNEL_VERSION(4,5,0)) > > Which will cause 4.4.256 to now change the result of that comparison. Sure, but there are no in-kernel users like this, so my sympathy is quite low :)