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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id BE302C433EF for ; Tue, 24 May 2022 21:16:48 +0000 (UTC) Received: from localhost ([::1]:35450 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ntbtW-0001J9-HA for qemu-devel@archiver.kernel.org; Tue, 24 May 2022 17:16:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41026) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ntbrT-0007po-Qk for qemu-devel@nongnu.org; Tue, 24 May 2022 17:14:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:50733) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ntbrQ-00046z-LA for qemu-devel@nongnu.org; Tue, 24 May 2022 17:14:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1653426875; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AC4sRrE7OzkgNdxcJQaHUMq3jFgoSWrf+jSxm51BweM=; b=FKEkKVzLCRIJ5C4nKkckhwJI++QrMYISmQJv8B4C/ZLndpGkkQOXOO0c/QxWiGc+gKnpE6 mg05Vdj9zZkpczpBPab1Ahg8bkO8YxULscwen5MVA+rAEuPA+rM4IQ99KFNBz/G6erCH5n 0bLuIpDH6KzwVpb5fi73T4TSUx9mX7Y= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-321-VPz1rK5FPmSqs58XjpFJcw-1; Tue, 24 May 2022 17:14:34 -0400 X-MC-Unique: VPz1rK5FPmSqs58XjpFJcw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AF326185A7A4; Tue, 24 May 2022 21:14:33 +0000 (UTC) Received: from redhat.com (unknown [10.2.16.148]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D130D2166B29; Tue, 24 May 2022 21:14:32 +0000 (UTC) Date: Tue, 24 May 2022 16:14:31 -0500 From: Eric Blake To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , qemu-block@nongnu.org, Stefan Hajnoczi , Hailiang Zhang , Juan Quintela , Fam Zheng Subject: Re: [PATCH 01/20] io: add a QIOChannelNull equivalent to /dev/null Message-ID: <20220524211406.hskzsft3qezuepfp@redhat.com> References: <20220524110235.145079-1-berrange@redhat.com> <20220524110235.145079-2-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220524110235.145079-2-berrange@redhat.com> User-Agent: NeoMutt/20220429-77-e284d5 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, May 24, 2022 at 12:02:16PM +0100, Daniel P. Berrangé wrote: > This is for code which needs a portable equivalent to a QIOChannelFile > connected to /dev/null. > > Signed-off-by: Daniel P. Berrangé > --- > include/io/channel-null.h | 55 +++++++ > io/channel-null.c | 237 ++++++++++++++++++++++++++++++ > io/meson.build | 1 + > io/trace-events | 3 + > tests/unit/meson.build | 1 + > tests/unit/test-io-channel-null.c | 95 ++++++++++++ > 6 files changed, 392 insertions(+) > create mode 100644 include/io/channel-null.h > create mode 100644 io/channel-null.c > create mode 100644 tests/unit/test-io-channel-null.c > +/** > + * QIOChannelNull: > + * > + * The QIOChannelNull object provides a channel implementation > + * that discards all writes and returns zero bytes for all reads. That describes the behavior of /dev/zero, not /dev/null, where reads always fail with EOF. > + */ > + > +struct QIOChannelNull { > + QIOChannel parent; > + bool closed; > +}; > + > diff --git a/io/channel-null.c b/io/channel-null.c > + > +static ssize_t > +qio_channel_null_readv(QIOChannel *ioc, > + const struct iovec *iov, > + size_t niov, > + int **fds G_GNUC_UNUSED, > + size_t *nfds G_GNUC_UNUSED, > + Error **errp) > +{ > + QIOChannelNull *nioc = QIO_CHANNEL_NULL(ioc); > + > + if (nioc->closed) { > + error_setg_errno(errp, EINVAL, > + "Channel is closed"); > + return -1; > + } > + > + return 0; > +} But this behavior is returning early EOF instead of using iov_memset() to read all zeroes the way /dev/zero would. > +++ b/tests/unit/test-io-channel-null.c > +static void test_io_channel_null_io(void) > +{ > + g_autoptr(QIOChannelNull) null = qio_channel_null_new(); > + char buf[1024]; > + GIOCondition gotcond = 0; > + Error *local_err = NULL; > + > + g_assert(qio_channel_write(QIO_CHANNEL(null), > + "Hello World", 11, > + &error_abort) == 11); I still cringe seeing tests inside g_assert(), but this is not the first instance of it. > + > + g_assert(qio_channel_read(QIO_CHANNEL(null), > + buf, sizeof(buf), > + &error_abort) == 0); Okay, you're testing for /dev/null behavior of early EOF. Other than misleading comments, this looks reasonable. But those comments are core enough as to what this channel does that I don't feel comfortable giving R-b yet. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org