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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 7955CC10F27 for ; Wed, 11 Mar 2020 12:30:43 +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 39CB120873 for ; Wed, 11 Mar 2020 12:30:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ntrbsvr0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39CB120873 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]:50910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jC0VW-0002sf-Cr for qemu-devel@archiver.kernel.org; Wed, 11 Mar 2020 08:30:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43749) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jC0US-00022M-B9 for qemu-devel@nongnu.org; Wed, 11 Mar 2020 08:29:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jC0UR-0006Zf-7D for qemu-devel@nongnu.org; Wed, 11 Mar 2020 08:29:36 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:57215 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jC0UR-0006ZN-4I for qemu-devel@nongnu.org; Wed, 11 Mar 2020 08:29:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583929774; 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=PCuibaYC6ojR/kYXj+gnirgJLuQUZGQYHGxrLbAL92s=; b=Ntrbsvr0lfJxQGprGh5X3Q4ttjLhgfBvBPL8dDMIH/bMza/KZ/cSTKsrZGil83ddtyQQDg PqtWcq2vGjrxqs4PqTgL5roaE8AL7dv/ozNBu0MUG2Jhf3MdubDRZCrwi5xPLW6OgmuzWo Q7RDJLreM+HhRkinsoCYji+daB/hmIE= 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-430-BgJV0j2kODaOWRBUFdj0Hw-1; Wed, 11 Mar 2020 08:29:30 -0400 X-MC-Unique: BgJV0j2kODaOWRBUFdj0Hw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3BCDD477; Wed, 11 Mar 2020 12:29:29 +0000 (UTC) Received: from [10.3.116.177] (ovpn-116-177.phx2.redhat.com [10.3.116.177]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B400690519; Wed, 11 Mar 2020 12:29:28 +0000 (UTC) Subject: Re: [PATCH 3/3] block: fail on open when file size is unaligned to request_alignment To: Max Reitz , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200130152218.7600-1-vsementsov@virtuozzo.com> <20200130152218.7600-4-vsementsov@virtuozzo.com> <4fb7d692-4009-c6a7-c765-292ac8073ae3@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <186c8080-a45b-0756-fa4d-c38af02f3a8b@redhat.com> Date: Wed, 11 Mar 2020 07:29:28 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <4fb7d692-4009-c6a7-c765-292ac8073ae3@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/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: kwolf@redhat.com, den@openvz.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/11/20 6:06 AM, Max Reitz wrote: > On 30.01.20 16:22, Vladimir Sementsov-Ogievskiy wrote: >> Prior to the commit the following command lead to crash: >> >> ./qemu-io --image-opts -c 'write 0 512' \ >> driver=3Dblkdebug,align=3D4096,image.driver=3Dnull-co,image.size=3D51= 2 >> >> It failes on assertion in bdrv_aligned_pwritev: >> "end_sector <=3D bs->total_sectors || child->perm & BLK_PERM_RESIZE" >> >> The problem is obvious: 512 is aligned to 4096 and becomes larger than >> file size. And the core bad thing is that file size is unaligned to >> request_alignment. >> >> Let's catch such case on bdrv_open_driver and fail. >=20 > I think we had a discussion on this before, but I can=92t find it right > now. (Although I think that had more to do with something in the > file-posix driver, because it wasn=92t limited to alignments above 512.) >=20 > In any case, the file itself is totally valid. Most importantly, qcow2 > will regularly create files with unaligned file lengths. >=20 > So let me create a qcow2 image on a 4k-aligned device: >=20 > $ truncate 512M fs.img > $ sudo losetup -f --show -b 4096 fs.img > /dev/loop0 > $ sudo mkfs.ext4 /dev/loop0 > [...] > $ sudo mount /dev/loop0 /mnt/tmp >=20 > $ sudo ./qemu-img create -f qcow2 /mnt/tmp/foo.qcow2 64M > Formatting '/mnt/tmp/foo.qcow2', fmt=3Dqcow2 size=3D67108864 > cluster_size=3D65536 lazy_refcounts=3Doff refcount_bits=3D16 > $ sudo ./qemu-io -t none -c quit /mnt/tmp/foo.qcow2 > qemu-io: can't open device /mnt/tmp/foo.qcow2: File size is unaligned to > request alignment >=20 > Which is too bad. >=20 > So the real solution would probably... Be to align the file size up to > the alignment? Or to bite the bullet and finally implement byte-accurate size=20 everywhere (instead of our current insistence on rounding size up to=20 512-byte multiples). If we have to deal with unaligned tails anyways,=20 it's better to make the code universally applicable whether that=20 unaligned tail is to 512 or to 4k, than to have it work for 512 but to=20 fail for 4k. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org