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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 74DEDC8300C for ; Tue, 28 Apr 2020 14:10:27 +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 0BBE5206F0 for ; Tue, 28 Apr 2020 14:10:26 +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="WgTwngU9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BBE5206F0 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]:59572 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jTQwL-0004IP-Qs for qemu-devel@archiver.kernel.org; Tue, 28 Apr 2020 10:10:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41340) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jTQvH-0002d9-C0 for qemu-devel@nongnu.org; Tue, 28 Apr 2020 10:09:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jTQta-0002ZT-WD for qemu-devel@nongnu.org; Tue, 28 Apr 2020 10:09:19 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:43786 helo=us-smtp-delivery-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 1jTQta-0002Z7-Iv for qemu-devel@nongnu.org; Tue, 28 Apr 2020 10:07:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588082853; 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=0dWzpIFE/w8Bjg5V5yKk030wUo8PY9TZh0NLdEkfm18=; b=WgTwngU91YWX+2lMxUvi3Z/V1JINYr6sIMNoxT1ew4di/p1U6r6JRg1cABfjFwqLFJ5mxO jNRhrYrde8cWCKyYzuf325B3nekNWBvueOxU9qRdcps0OOdsWmy3yTsGjDHx3aEnp43ObV X8b/+hIs2yFYHQ5nExcCreHIF08QJYY= 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-312-1DpqChjmMciXjTGZ7PRW0Q-1; Tue, 28 Apr 2020 10:07:31 -0400 X-MC-Unique: 1DpqChjmMciXjTGZ7PRW0Q-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 05B608064DF; Tue, 28 Apr 2020 14:07:31 +0000 (UTC) Received: from [10.10.116.80] (ovpn-116-80.rdu2.redhat.com [10.10.116.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3E704610AB; Tue, 28 Apr 2020 14:07:29 +0000 (UTC) Subject: Re: [PATCH 1/4] block: Add bdrv_make_empty() To: Kevin Wolf References: <20200428132629.796753-1-mreitz@redhat.com> <20200428132629.796753-2-mreitz@redhat.com> <20200428140132.GF5789@linux.fritz.box> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Tue, 28 Apr 2020 09:07:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200428140132.GF5789@linux.fritz.box> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/28 02:06:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/28/20 9:01 AM, Kevin Wolf wrote: >> Can we please fix this to take a flags parameter? I want to make it easier >> for callers to request BDRV_REQ_NO_FALLBACK for distinguishing between >> callers where the image must be made empty (read as all zeroes) regardless >> of time spent, vs. made empty quickly (including if it is already all zero) >> but where the caller is prepared for the operation to fail and will write >> zeroes itself if fast bulk zeroing was not possible. > > bdrv_make_empty() is not for making an image read as all zeroes, but to > make it fully unallocated so that the backing file becomes visible. > > Are you confusing it with bdrv_make_zero(), which is just a wrapper > around bdrv_pwrite_zeroes() and does take flags? Yes. Although now I'm wondering if the two should remain separate or should just be a single driver callback where flags can include BDRV_REQ_ZERO_WRITE to distinguish whether exposing the backing file vs. reading as all zeroes is intended, or if that is merging too much. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org