Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754747AbbGQS4X (ORCPT ); Fri, 17 Jul 2015 14:56:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60650 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752375AbbGQS4V (ORCPT ); Fri, 17 Jul 2015 14:56:21 -0400 Date: Fri, 17 Jul 2015 20:54:34 +0200 From: Oleg Nesterov To: Austin S Hemmelgarn Cc: Benjamin LaHaise , Andrew Morton , Joonsoo Kim , Fengguang Wu , Jeff Moyer , Johannes Weiner , Stephen Rothwell , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm-move-mremap-from-file_operations-to-vm_operations_struct-fix Message-ID: <20150717185434.GA2290@redhat.com> References: <20150716231405.GA25147@redhat.com> <20150716162444.26425f5e227387f1166a6d16@linux-foundation.org> <20150716235227.GA26551@redhat.com> <20150717140615.GA2779@kvack.org> <20150717172726.GA30443@redhat.com> <20150717173757.GD2779@kvack.org> <20150717175542.GA31888@redhat.com> <55A94578.5050306@gmail.com> <20150717181940.GA946@redhat.com> <55A94BD2.5040603@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55A94BD2.5040603@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1872 Lines: 54 On 07/17, Austin S Hemmelgarn wrote: > > On 2015-07-17 14:19, Oleg Nesterov wrote: >> On 07/17, Austin S Hemmelgarn wrote: >>> >>> On 2015-07-17 13:55, Oleg Nesterov wrote: >>>> On 07/17, Benjamin LaHaise wrote: >>>>> >>>>> Don't add BUG(). It's the equivalent approach of saying "I think this code >>>>> isn't needed, but I'm lazy and not going to remove it properly." >>>> >>>> There is another interpretation: I think this code must be never called, >>>> if it is actually called we have a serious problem which should be loudly >>>> reported. >>>> >>> And not compiling it at all _will_ loudly report it, it'll just report >>> it during linking instead of at run-time, which is a much better time to >>> shout about it. >> >> And how can we do this? >> > If a function that isn't defined (for example, you use a #if block to > comment it out under certain circumstances), then the link will fail > rather noisily something references it. This is what we are trying to fix. > We already know during the > compile that it's a NOMMU kernel, so anything that calls it on a MMU > enabled kernel can have a compile time check added It already has. memory.c is not compiled if NOMMU. The problem is aio_ring_vm_ops which references this function. And btw filemap_fault() too. And just in case, I won't mind to add ifdef(CONFIG_MMU) there, I am waiting for reply from Benjamin. > instead of doing the > check at runtime (or even just calling it without checking), thus even > further reducing code size. So what exactly do you suggest to fix the problem? I agree with any solution which satisfies the maintainers. Oleg. -- 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/