From owner-svn-src-all@freebsd.org Sat Jun 15 15:59:46 2019 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 41D1915CA5EE; Sat, 15 Jun 2019 15:59:46 +0000 (UTC) (envelope-from marius@alchemy.franken.de) Received: from alchemy.franken.de (alchemy.franken.de [194.94.249.214]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "alchemy.franken.de", Issuer "alchemy.franken.de" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id B62AE8181F; Sat, 15 Jun 2019 15:59:45 +0000 (UTC) (envelope-from marius@alchemy.franken.de) Received: from alchemy.franken.de (localhost [127.0.0.1]) by alchemy.franken.de (8.15.2/8.15.2/ALCHEMY.FRANKEN.DE) with ESMTPS id x5FFxexk032360 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sat, 15 Jun 2019 17:59:40 +0200 (CEST) (envelope-from marius@alchemy.franken.de) Received: (from marius@localhost) by alchemy.franken.de (8.15.2/8.15.2/Submit) id x5FFxedV032359; Sat, 15 Jun 2019 17:59:40 +0200 (CEST) (envelope-from marius) Date: Sat, 15 Jun 2019 17:59:40 +0200 From: Marius Strobl To: Andrew Gallatin Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r349055 - head/sys/net Message-ID: <20190615155940.GM6782@alchemy.franken.de> References: <201906151107.x5FB7f6N039968@repo.freebsd.org> <154077cb-14b1-1dbc-cb65-3233045963c0@cs.duke.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <154077cb-14b1-1dbc-cb65-3233045963c0@cs.duke.edu> User-Agent: Mutt/1.9.2 (2017-12-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (alchemy.franken.de [0.0.0.0]); Sat, 15 Jun 2019 17:59:40 +0200 (CEST) X-Rspamd-Queue-Id: B62AE8181F X-Spamd-Bar: ------ Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-6.96 / 15.00]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; REPLY(-4.00)[]; NEURAL_HAM_SHORT(-0.96)[-0.964,0] X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 15 Jun 2019 15:59:46 -0000 On Sat, Jun 15, 2019 at 09:08:05AM -0400, Andrew Gallatin wrote: > On 2019-06-15 07:07, Marius Strobl wrote: > > Author: marius > > Date: Sat Jun 15 11:07:41 2019 > > New Revision: 349055 > > > Log: > > - Replace unused and only ever written to members of public iflib(9) > > structs with placeholders (in the latter case, IFLIB_MAX_TX_BYTES > > etc. are also only ever used for these write-only members if at all, > > so both these macros and members can just go). Using these spares > > may render it possible to merge certain iflib(9) fixes to stable/12. > > Otherwise, changes extending struct if_irq or struct if_shared_ctx > > in any way would break KBI as instances of these are allocated by > > the driver front-ends (by contrast, struct if_pkt_info as well as > > struct if_softc_ctx instances are provided by iflib(9) and, thus, > > may grow at least at the end without breaking KBI). > > Given the above, why replace ipi_tcp_sum in if_pkt_info with a spare? > Given that if_pkt_info can grow, I would also expect it to be able to > shrink. So I don't quite see why the spare is needed here. > > I also worry about carrying the other spares around forever. Yes, KBI-wise it should be also safe for instances of structures allocated by iflib(9) to shrink at the end (though shrinking structures usually isn't a concern when MFCing as such parts may just be omitted); changes altering the offsets of members would be a problem regarding KBI. Still, I don't like changing the size of publicly visible structures in stable branches without a real good reason even if such a change doesn't strictly break the KBI. So the plan is to MFC the spares but then to get rid of the ones whose removal doesn't break KBI in head. Marius