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=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 E6941C433E0 for ; Mon, 18 Jan 2021 13:42:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FC5920E65 for ; Mon, 18 Jan 2021 13:42:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404669AbhARNmR (ORCPT ); Mon, 18 Jan 2021 08:42:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:37382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404697AbhARNk4 (ORCPT ); Mon, 18 Jan 2021 08:40:56 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 030FA2065E; Mon, 18 Jan 2021 13:40:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610977201; bh=+hQ/DQfrKXADkEoj0kzneLBbQSy5clevR8ljdD3I8DA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XJNW+Ombn7kHROG7crCO5CxWLDsEhG+hq9RJUgowONq56+Wh8LPDNp6zeYYnOKiRg +3WbO1xhJn0jXbMIiYI9T5DS0t3nqgXmzETspZXZw2Ccyyv+69WBHRCZREySY+RSXv Rd11mkbO9w2UwmQH2Q+W3IEcACOJruG2Uwdjkqv+y86t+39CDWsXGysIF6zfTC1bCX YuBe9hJulZKY+ae76IWdbkP7D6sr52gY3DjBSddrZlETbgh7P12vfR9ru6nAJnUquU V1krPdnYvMLfCcfVcdIewUTJKeljWu+jn1DjnCze975LPbiAWOB6sWhApBq807thBE J4AZq9I+w6YYw== Date: Mon, 18 Jan 2021 08:39:59 -0500 From: Sasha Levin To: Greg KH 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: <20210118133959.GZ4035784@sasha-vm> References: <20210118014951.250815-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Thanks, Sasha