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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 9BD2DC3A59E for ; Mon, 2 Sep 2019 13:34:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 73C49216C8 for ; Mon, 2 Sep 2019 13:34:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73C49216C8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36646 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i4mTF-0001vy-Gx for qemu-devel@archiver.kernel.org; Mon, 02 Sep 2019 09:34:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52343) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i4mRh-00011R-43 for qemu-devel@nongnu.org; Mon, 02 Sep 2019 09:32:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i4mRc-0002Mu-Nn for qemu-devel@nongnu.org; Mon, 02 Sep 2019 09:32:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38412) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i4mRW-00027y-VL; Mon, 02 Sep 2019 09:32:27 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0237D3082E10; Mon, 2 Sep 2019 13:32:25 +0000 (UTC) Received: from localhost.localdomain (ovpn-116-189.ams2.redhat.com [10.36.116.189]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 76EA810016EB; Mon, 2 Sep 2019 13:32:21 +0000 (UTC) Date: Mon, 2 Sep 2019 15:32:20 +0200 From: Kevin Wolf To: Max Reitz Message-ID: <20190902133219.GG13140@localhost.localdomain> References: <20190823184733.18929-1-mreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190823184733.18929-1-mreitz@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Mon, 02 Sep 2019 13:32:25 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 0/2] block: Let blockdev-create return 0 on success X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 23.08.2019 um 20:47 hat Max Reitz geschrieben: > Jobs are expected to return 0 on success. .bdrv_co_create() on the > other hand is a block layer function, and as such returns a > non-negative value on success. I don't agree that >= 0 is the block layer way. The block layer uses 0/-errno for the largest part of its interfaces; and I think the BlockDriver callbacks might even be consistent in this. Of course, we never documented this anywhere, maybe we should... The only historical exceptions I'm aware of are blk/bdrv_pread/pwrite(), which return the byte count instead of 0. They should be fixed eventually, but it just never seemed important enough, even though it did cause bugs every now and then. > blockdev_create_run() should translate between the two (patch 1). > > Without patch 1, blockdev-create is likely to fail for VPC images. > Hence patch 2. I'd argue this is a VPC bug. In the success path, it shouldn't return ret as it happens to be at the end (it comes from bdrv_pwrite()), but set it to 0 right before the 'fail:' label. This is really a regression Jeff introduced in commit fef6070eff2, though the bug was only latent then (five years ago). Kevin