From patchwork Fri Sep 8 09:44:57 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fam Zheng X-Patchwork-Id: 811427 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xpXWt4Q9Zz9s81 for ; Fri, 8 Sep 2017 19:46:18 +1000 (AEST) Received: from localhost ([::1]:44199 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dqFrc-0003Nl-Ou for incoming@patchwork.ozlabs.org; Fri, 08 Sep 2017 05:46:16 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38116) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dqFqk-0002zq-Dv for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:45:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dqFqc-0001Ah-QB for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:45:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40470) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dqFqP-0000lb-S4; Fri, 08 Sep 2017 05:45:01 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id DA69980F79; Fri, 8 Sep 2017 09:45:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com DA69980F79 Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=famz@redhat.com Received: from lemon.redhat.com (ovpn-12-98.pek2.redhat.com [10.72.12.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id ACA2960E3A; Fri, 8 Sep 2017 09:44:58 +0000 (UTC) From: Fam Zheng To: qemu-devel@nongnu.org Date: Fri, 8 Sep 2017 17:44:57 +0800 Message-Id: <20170908094457.25317-1-famz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 08 Sep 2017 09:45:01 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v3] file-posix: Clear out first sector in hdev_create X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" People get surprised when, after "qemu-img create -f raw /dev/sdX", they still see qcow2 with "qemu-img info", if previously the bdev had a qcow2 header. While this is natural because raw doesn't need to write any magic bytes during creation, hdev_create is free to clear out the first sector to make sure the stale qcow2 header doesn't cause such confusion. Signed-off-by: Fam Zheng --- v3: Don't do anything if there were errors. [Kevin] v2: Use stack allocated buffer. [Eric] Fix return value. (Keep qemu_write_full instead of switching to qemu_pwritev because the former handles short writes.) Fix typo "qemu-img". [Changlong] --- block/file-posix.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/block/file-posix.c b/block/file-posix.c index 6acbd56238..72ecfbb0e0 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2700,6 +2700,16 @@ static int hdev_create(const char *filename, QemuOpts *opts, ret = -ENOSPC; } + if (!ret && total_size) { + uint8_t buf[BDRV_SECTOR_SIZE] = { 0 }; + int64_t zero_size = MIN(BDRV_SECTOR_SIZE, total_size); + if (lseek(fd, 0, SEEK_SET) == -1) { + ret = -errno; + } else { + ret = qemu_write_full(fd, buf, zero_size); + ret = ret == zero_size ? 0 : -errno; + } + } qemu_close(fd); return ret; }