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=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 0CDE8C63777 for ; Fri, 20 Nov 2020 14:08:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7F362245B for ; Fri, 20 Nov 2020 14:08:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="jVlVn/G7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727694AbgKTOIq (ORCPT ); Fri, 20 Nov 2020 09:08:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:52509 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726561AbgKTOIq (ORCPT ); Fri, 20 Nov 2020 09:08:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605881324; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aGTiEL+52RoWS+9nd1Ms/clbRnrmeizFKg1laIg8ttk=; b=jVlVn/G72N0HCSwV9sN3r8VKcg7slmk/em9TWmkqHA1w7QOT4wFoJSLKWchHeFvvz8luEX yrRCwJEIggsc3QrbdxoogxduxMYu49tbtYsZqaHoJUl6cp9Ikb5ZgHjuzqvCkt/qr2Djdn jE3MlR+5WEmTypWywdmw5ADn2CWNJdQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-206-jDTPSWkfN9q9QjQ53M0X-Q-1; Fri, 20 Nov 2020 09:08:42 -0500 X-MC-Unique: jDTPSWkfN9q9QjQ53M0X-Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0F640814410; Fri, 20 Nov 2020 14:08:41 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7663519C46; Fri, 20 Nov 2020 14:08:37 +0000 (UTC) Date: Fri, 20 Nov 2020 09:08:20 -0500 From: Mike Snitzer To: Mikulas Patocka Cc: Randy Dunlap , Christian Borntraeger , linux-kernel@vger.kernel.org, Alasdair Kergon , dm-devel@redhat.com, Heiko Carstens , Vasily Gorbik , linux-s390@vger.kernel.org Subject: Re: md: dm-writeback: add __noreturn to BUG-ging function Message-ID: <20201120140819.GA7359@redhat.com> References: <20201113225228.20563-1-rdunlap@infradead.org> <344abf76-9405-58ba-2dc4-27cab88c974d@de.ibm.com> <20201117163147.GA27243@redhat.com> <20201118154944.GB545@redhat.com> <20201118160748.GA754@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 18 2020 at 4:24pm -0500, Mikulas Patocka wrote: > > > On Wed, 18 Nov 2020, Mike Snitzer wrote: > > > On Wed, Nov 18 2020 at 10:49am -0500, > > Mike Snitzer wrote: > > > > > I don't think my suggestion will help.. given it'd still leave > > > persistent_memory_claim() without a return statement. > > > > > > Think it worthwhile to just add a dummy 'return 0;' after the BUG(). > > > > Decided to go with this, now staged for 5.11: > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.11&id=a1e4865b4dda7071f3707f7e551289ead66e38b1 > > Hi > > I would just use "return -EOPNOTSUPP;" and drop the "#ifdef > DM_WRITECACHE_HAS_PMEM" that you added. > > That BUG/return -EOPNOTSUPP code can't happen at all - if > DM_WRITECACHE_HAS_PMEM is not defined, WC_MODE_PMEM(wc) always returns > false - so persistent_memory_claim and BUG() can't ever be called. And if > it can't be called, you don't need to add a code that prints an error in > that case. > > If we don't have DM_WRITECACHE_HAS_PMEM, the compiler optimizer will > remove all the code guarded with if (WC_MODE_PMEM(wc)) as unreachable. > > Mikulas Fair enough.