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=-9.4 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,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 DD5FBC433DF for ; Wed, 19 Aug 2020 20:14:11 +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 AA87B2078D for ; Wed, 19 Aug 2020 20:14:11 +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="NFuu/eW8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA87B2078D 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]:39786 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8UTK-000665-Vv for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 16:14:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57002) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8USm-0005cM-0B for qemu-devel@nongnu.org; Wed, 19 Aug 2020 16:13:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:24764 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k8USj-0006Zw-Jc for qemu-devel@nongnu.org; Wed, 19 Aug 2020 16:13:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597868012; 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=M9t6xTobedTdcP8an9TS0n+JJ3ErXI5SSQddN5XzHmw=; b=NFuu/eW8aeQizcOhz1Km9xNbHeXQDyL0yyyWRZhRNq7pJhuphq9+X+ieNED/qnv+/S4iVe a0LhRWw0u/Btik48m59Eu5hJWQKt5jnzJ9fypnBNt6IiZ/2vDdSmZ8PUhcdMWBCEKirbck pCedLcj2Pp9uNJ714KULKhIJQRV2mMg= 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-98-8Zu2_HP0Ou2ODcUMQCzohA-1; Wed, 19 Aug 2020 16:13:30 -0400 X-MC-Unique: 8Zu2_HP0Ou2ODcUMQCzohA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 494A21015DC4; Wed, 19 Aug 2020 20:13:29 +0000 (UTC) Received: from [10.3.112.136] (ovpn-112-136.phx2.redhat.com [10.3.112.136]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ECA2E6F120; Wed, 19 Aug 2020 20:13:28 +0000 (UTC) Subject: Re: [RFC PATCH 09/22] nbd: Add writethrough to block-export-add To: Kevin Wolf , qemu-block@nongnu.org References: <20200813162935.210070-1-kwolf@redhat.com> <20200813162935.210070-10-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <178271b2-e90e-8d85-3bda-403e16ffa91d@redhat.com> Date: Wed, 19 Aug 2020 15:13:28 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200813162935.210070-10-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=eblake@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/18 23:05:17 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/13/20 11:29 AM, Kevin Wolf wrote: > qemu-nbd allows use of writethrough cache modes, which mean that write > requests made through NBD will cause a flush before they complete. > Expose the same functionality in block-export-add. > > Signed-off-by: Kevin Wolf > --- > qapi/block-export.json | 7 ++++++- > blockdev-nbd.c | 2 +- > 2 files changed, 7 insertions(+), 2 deletions(-) > > +++ b/blockdev-nbd.c > @@ -218,7 +218,7 @@ BlockExport *nbd_export_create(BlockExportOptions *exp_args, Error **errp) > > exp = nbd_export_new(bs, arg->name, arg->description, arg->bitmap, > !arg->writable, !arg->writable, > - NULL, false, errp); > + NULL, exp_args->writethrough, errp); It would someday be nice to get rid of exp_args->has_writethrough in QAPI generated code, but that's independent of this series. Meanwhile, you are safe in relying on writethrough being false when has_writethrough is false. This change makes sense to me interface-wise. QAPI-wise, should we try harder to make writethrough settable only for writable exports (and an error for read-only exports)? I'm not sure what QAPI contortions would have to look like to make that enforced by the QMP parser; but it's also not the end of the world if we just always permit the optional field and then apply a post-parse semantic check. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org