Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932603Ab3FMHqn (ORCPT ); Thu, 13 Jun 2013 03:46:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45350 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755611Ab3FMHqm (ORCPT ); Thu, 13 Jun 2013 03:46:42 -0400 Date: Thu, 13 Jun 2013 10:30:47 +0300 From: "Michael S. Tsirkin" To: Rusty Russell Cc: Julia Lawall , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Thomas Meyer , grant.likely@linaro.org, rob.herring@calxeda.com, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [RFC] PTR_ERR: return 0 if ptr isn't an error value. Message-ID: <20130613073046.GB10326@redhat.com> References: <1370080565.29224.29.camel@localhost.localdomain> <87mwr8sz9g.fsf@rustcorp.com.au> <20130603071526.GA5483@pengutronix.de> <87mwquzkvf.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87mwquzkvf.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1705 Lines: 50 On Thu, Jun 13, 2013 at 02:07:40PM +0930, Rusty Russell wrote: > Julia Lawall writes: > > On Mon, 3 Jun 2013, Uwe Kleine-K?nig wrote: > > For a random example, here is a function that currently uses PTR_RET: > > Heheh, nice choice: I think I wrote that code originally :) > > > static int __net_init iptable_raw_net_init(struct net *net) > > { > > struct ipt_replace *repl; > > > > repl = ipt_alloc_initial_table(&packet_raw); > > if (repl == NULL) > > return -ENOMEM; > > net->ipv4.iptable_raw = > > ipt_register_table(net, &packet_raw, repl); > > kfree(repl); > > return PTR_RET(net->ipv4.iptable_raw); > > } > > > > If it becomes return PTR_ERR(...); at the end, won't it look like the > > function always fails? > > That is a valid point, though in this case the reader will know that > can't be the case. > > On the other hand, there's an incremental learning curve cost to every > convenience function we add. There are only 50 places where we use > PTR_RET(), so it's not saving us very much typing over the clearest > solution: open-coding the test. > > I think using PTR_ERR() is a less bad solution than promoting PTR_RET, > which has a non-obvious name. > > Cheers, > Rusty. Will a longer name make the function more obvious? PTR_ERR_OR_ZERO() ? PTR_ERR0() ? PTR_ERR() can then stay simple for cases where we know we are on the error path. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/