From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lars Ellenberg Subject: Re: [PATCH net-next v2] block/drbd: use nla_put_u64_64bit() Date: Wed, 4 May 2016 11:05:30 +0200 Message-ID: <20160504090529.GJ16459@soda.linbit> References: <57286F49.8050107@6wind.com> <1462268358-19044-1-git-send-email-nicolas.dichtel@6wind.com> <20160503100644.GE16459@soda.linbit> <20160503.120556.1317913903199470646.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, nicolas.dichtel-pdR9zngts4EAvxtiuMwx3w@public.gmane.org, philipp.reisner-63ez5xqkn6DQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org To: David Miller Return-path: Content-Disposition: inline In-Reply-To: <20160503.120556.1317913903199470646.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: drbd-dev-bounces-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org Errors-To: drbd-dev-bounces-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org List-Id: netdev.vger.kernel.org On Tue, May 03, 2016 at 12:05:56PM -0400, David Miller wrote: > From: Lars Ellenberg > Date: Tue, 3 May 2016 12:06:44 +0200 > > > Please just NOT use an additional "field", > > but always use 0 to pad. > > You can't, it doesn't work. I did, and it *did* work. At least, it appeared to. I'm not talking about every user of netlink out there. That I don't know. But specifically for DRBD netlink, from what my experiments tell me, it works just fine. > We are adding a new field to every netlink protocol family that has > this alignment problem. We don't have an "alignment problem" there, btw. Last time I checked, we did work fine without this alignment magic, we already take care of that, yes, even on affected architectures. On Tue, May 03, 2016 at 12:06:52PM -0400, David Miller wrote: > From: Lars Ellenberg > Date: Tue, 3 May 2016 12:06:44 +0200 > > > Whereas using some arbitrary value will be wrong, > > and will needlessly break userland. > > It cannot break userland. It can, if those tags have been used already. There is DRBD out-of-tree as well, it usually is ahead of in-tree DRBD. But yes, I could obviously check and assign and reserve some not-yet-used tag to all of them. I don't see why, though, given that 0 (appearently) works fine. Can you elaborate why and how that does not work? Lars