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=-9.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 086A4C433DF for ; Mon, 19 Oct 2020 15:47:48 +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 4FC882075E for ; Mon, 19 Oct 2020 15:47:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NEh8Bz+j" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4FC882075E 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]:40116 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kUXNy-0005oi-6Y for qemu-devel@archiver.kernel.org; Mon, 19 Oct 2020 11:47:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49884) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kUXMi-0004Uf-T3 for qemu-devel@nongnu.org; Mon, 19 Oct 2020 11:46:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:48328) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kUXMY-0007RI-Jb for qemu-devel@nongnu.org; Mon, 19 Oct 2020 11:46:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603122376; 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=GM/hkbbFTg87YpTuUb7kAfPMdPJHFhSNSNZgTBR5Ibc=; b=NEh8Bz+jy4w8MtCIofbrmF1Ywm92AFBHDp6gEEF5dVnB1FzlPTowyFZOwjfEwm3ijQkm9p ejK6/+A9oeLU2zpyNmkdnOOXJwF6SQWSq4kN3YM+fokTWPAJLUIPJB1lx9/cr1i9rN1KiH fZlsQudZCBK2AdrLJAVj4e9LFQOtgxg= 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-348-meYMcs6mM16ic8SxuO3mcw-1; Mon, 19 Oct 2020 11:46:13 -0400 X-MC-Unique: meYMcs6mM16ic8SxuO3mcw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B139F6409B; Mon, 19 Oct 2020 15:46:10 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-182.ams2.redhat.com [10.36.112.182]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9858260C05; Mon, 19 Oct 2020 15:46:01 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E34B51132A08; Mon, 19 Oct 2020 17:45:59 +0200 (CEST) From: Markus Armbruster To: Kevin Wolf Subject: Re: [PATCH v3 02/13] block: use return status of bdrv_append() References: <20201016171057.6182-1-vsementsov@virtuozzo.com> <20201016171057.6182-3-vsementsov@virtuozzo.com> <20201019121302.GD6508@merkur.fritz.box> Date: Mon, 19 Oct 2020 17:45:59 +0200 In-Reply-To: <20201019121302.GD6508@merkur.fritz.box> (Kevin Wolf's message of "Mon, 19 Oct 2020 14:13:02 +0200") Message-ID: <87v9f62p8o.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=63.128.21.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/19 02:32:01 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: Vladimir Sementsov-Ogievskiy , berto@igalia.com, stefanha@redhat.com, qemu-block@nongnu.org, Greg Kurz , qemu-devel@nongnu.org, pavel.dovgaluk@ispras.ru, pbonzini@redhat.com, den@openvz.org, mreitz@redhat.com, jsnow@redhat.com, ari@tuxera.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Kevin Wolf writes: > Am 16.10.2020 um 19:10 hat Vladimir Sementsov-Ogievskiy geschrieben: >> Now bdrv_append returns status and we can drop all the local_err things >> around it. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy >> Reviewed-by: Greg Kurz >> Reviewed-by: Alberto Garcia >> --- >> block.c | 5 +---- >> block/backup-top.c | 20 ++++++++------------ >> block/commit.c | 5 +---- >> block/mirror.c | 6 ++---- >> blockdev.c | 4 +--- >> tests/test-bdrv-graph-mod.c | 6 +++--- >> 6 files changed, 16 insertions(+), 30 deletions(-) >> >> diff --git a/block.c b/block.c >> index b05fbff42d..7b6818c681 100644 >> --- a/block.c >> +++ b/block.c >> @@ -3161,7 +3161,6 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, >> int64_t total_size; >> QemuOpts *opts = NULL; >> BlockDriverState *bs_snapshot = NULL; >> - Error *local_err = NULL; >> int ret; >> >> /* if snapshot, we create a temporary backing file and open it >> @@ -3208,9 +3207,7 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, >> * order to be able to return one, we have to increase >> * bs_snapshot's refcount here */ >> bdrv_ref(bs_snapshot); >> - bdrv_append(bs_snapshot, bs, &local_err); >> - if (local_err) { >> - error_propagate(errp, local_err); >> + if (bdrv_append(bs_snapshot, bs, errp) < 0) { > > We generally avoid calling functions with side effects inside a > comparison. Let's use the usual pattern: > > ret = bdrv_append(bs_snapshot, bs, errp); > if (ret < 0) { > ... > } I'd also advice against buring side effects too deep, but calling a function in a failure-checking conditional is pretty benign. It's also common: $ git-grep 'if ([a-z].*) < 0) {' coughs up several hundred instances. That said, there is none in block.c. Local consistency matters. [...]