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 E9911C5519F for ; Fri, 20 Nov 2020 14:09:02 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 654782223F for ; Fri, 20 Nov 2020 14:09:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="L7e7Mu0S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 654782223F Authentication-Results: mail.kernel.org; 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Fri, 20 Nov 2020 14:08:50 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B56225D6AD; Fri, 20 Nov 2020 14:08:49 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id BD42C180954D; Fri, 20 Nov 2020 14:08:42 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 0AKE8fb9002664 for ; Fri, 20 Nov 2020 09:08:41 -0500 Received: by smtp.corp.redhat.com (Postfix) id 0DA9C19D80; 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 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 In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-loop: dm-devel@redhat.com Cc: linux-s390@vger.kernel.org, Vasily Gorbik , Heiko Carstens , Randy Dunlap , linux-kernel@vger.kernel.org, Christian Borntraeger , dm-devel@redhat.com, Alasdair Kergon Subject: Re: [dm-devel] md: dm-writeback: add __noreturn to BUG-ging function X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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. -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:49303 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726561AbgKTOIr (ORCPT ); Fri, 20 Nov 2020 09:08:47 -0500 Date: Fri, 20 Nov 2020 09:08:20 -0500 From: Mike Snitzer 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: List-ID: 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 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.