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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 A01F7C433E0 for ; Thu, 7 Jan 2021 10:00:00 +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 0C7CB22248 for ; Thu, 7 Jan 2021 09:59:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0C7CB22248 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]:51290 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kxS5G-0008Dv-NS for qemu-devel@archiver.kernel.org; Thu, 07 Jan 2021 04:59:58 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34346) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kxS3v-0007iD-0z for qemu-devel@nongnu.org; Thu, 07 Jan 2021 04:58:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:24638) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kxS3r-0003jn-Hu for qemu-devel@nongnu.org; Thu, 07 Jan 2021 04:58:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610013508; 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=aEU5MZcMQhymtuikXuLy9TJeQJ18+FbBlbhpoPJd/2k=; b=dFW+61gBE1Jq+3kcUMApJSvku1juhb5EJK+Auosdj+vw2FgUae7ltGp3WcMuDD9QixQfkc S1AVkEPCSr7kMbhxaZjol/A1Hsxml6I3D9LNZfnGugkA6fmPunG5A9CG7mJFSHxKDSxzOc VtWIPo08Zc+ZPUt/FCEv7zSW5Ye7A1w= 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-17-um7aYS99PrOs8FqlQnKnjg-1; Thu, 07 Jan 2021 04:58:24 -0500 X-MC-Unique: um7aYS99PrOs8FqlQnKnjg-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 626C4803623; Thu, 7 Jan 2021 09:58:22 +0000 (UTC) Received: from localhost (ovpn-114-98.ams2.redhat.com [10.36.114.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id 772831346D; Thu, 7 Jan 2021 09:58:18 +0000 (UTC) Date: Thu, 7 Jan 2021 09:58:17 +0000 From: "Richard W.M. Jones" To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 4/4] block: introduce BDRV_MAX_LENGTH Message-ID: <20210107095817.GA2673@redhat.com> References: <20201203222713.13507-1-vsementsov@virtuozzo.com> <20201203222713.13507-5-vsementsov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <20201203222713.13507-5-vsementsov@virtuozzo.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=rjones@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=rjones@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.252, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: fam@euphon.net, kwolf@redhat.com, berto@igalia.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Dec 04, 2020 at 01:27:13AM +0300, Vladimir Sementsov-Ogievskiy wrote: > Finally to be safe with calculations, to not calculate different > maximums for different nodes (depending on cluster size and > request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30) > as absolute maximum bytes length for Qemu. Actually, it's not much less > than INT64_MAX. > +/* > + * We want allow aligning requests and disk length up to any 32bit alignment > + * and don't afraid of overflow. > + * To achieve it, and in the same time use some pretty number as maximum disk > + * size, let's define maximum "length" (a limit for any offset/bytes request and > + * for disk size) to be the greatest power of 2 less than INT64_MAX. > + */ > +#define BDRV_MAX_ALIGNMENT (1L << 30) > +#define BDRV_MAX_LENGTH (QEMU_ALIGN_DOWN(INT64_MAX, BDRV_MAX_ALIGNMENT)) This change broke nbdkit tests. We test that qemu can handle a qemu NBD export of size 2^63 - 512, the largest size that (experimentally) we found qemu could safely handle. eg: https://github.com/libguestfs/nbdkit/blob/master/tests/test-memory-largest-for-qemu.sh Before this commit: $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' image: nbd://localhost:10809 file format: raw virtual size: 8 EiB (9223372036854775296 bytes) disk size: unavailable After this commit: $ nbdkit memory $(( 2**63 - 512 )) --run './qemu-img info "$uri"' qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large Can I confirm that this limit is now the new official one and we should adjust nbdkit tests? Or was this change unintentional given that qemu seemed happy to handle 2^63 - 512 disks before? Note that nbdkit & libnbd support up to 2^63 - 1 bytes (we are not limited to whole sectors). Also the Linux kernel will let you create a /dev/nbdX device of size 2^63 - 1. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org