From patchwork Fri Aug 11 08:09:39 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fam Zheng X-Patchwork-Id: 800457 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 3xTHkh5X1Pz9sDB for ; Fri, 11 Aug 2017 18:10:52 +1000 (AEST) Received: from localhost ([::1]:46946 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dg51u-0006qQ-IT for incoming@patchwork.ozlabs.org; Fri, 11 Aug 2017 04:10:50 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43268) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dg50z-0006Rk-Gn for qemu-devel@nongnu.org; Fri, 11 Aug 2017 04:09:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dg50y-0005jj-E4 for qemu-devel@nongnu.org; Fri, 11 Aug 2017 04:09:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60254) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dg50r-0005fW-Uw; Fri, 11 Aug 2017 04:09:46 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id BFE43C05A1A1; Fri, 11 Aug 2017 08:09:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com BFE43C05A1A1 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=famz@redhat.com Received: from lemon.redhat.com (ovpn-12-60.pek2.redhat.com [10.72.12.60]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8772360606; Fri, 11 Aug 2017 08:09:40 +0000 (UTC) From: Fam Zheng To: qemu-devel@nongnu.org Date: Fri, 11 Aug 2017 16:09:39 +0800 Message-Id: <20170811080939.22304-1-famz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 11 Aug 2017 08:09:42 +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 for-2.11 v2] 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 Reviewed-by: Eric Blake --- 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 f4de022ae0..a63bbf2b90 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2703,6 +2703,16 @@ static int hdev_create(const char *filename, QemuOpts *opts, ret = -ENOSPC; } + if (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; }