From nobody Tue Feb 10 04:12:47 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1511187199452590.5290196383487; Mon, 20 Nov 2017 06:13:19 -0800 (PST) Received: from localhost ([::1]:57538 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGmp2-0004F4-De for importer@patchew.org; Mon, 20 Nov 2017 09:13:16 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59310) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGmnl-0003bm-Oq for qemu-devel@nongnu.org; Mon, 20 Nov 2017 09:11:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eGmnk-0004dX-Um for qemu-devel@nongnu.org; Mon, 20 Nov 2017 09:11:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44612) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eGmng-0004Yb-Id; Mon, 20 Nov 2017 09:11:52 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BE4946A7EB; Mon, 20 Nov 2017 14:11:51 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-116-185.ams2.redhat.com [10.36.116.185]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9B8334F9EF; Mon, 20 Nov 2017 14:11:49 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 20 Nov 2017 15:11:40 +0100 Message-Id: <20171120141141.24626-2-kwolf@redhat.com> In-Reply-To: <20171120141141.24626-1-kwolf@redhat.com> References: <20171120141141.24626-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 20 Nov 2017 14:11:51 +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 1/2] block: Don't use BLK_PERM_CONSISTENT_READ for format probing 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: kwolf@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" For format probing, we don't really care whether all of the image content is consistent. The only thing we're looking at is the image header, and specifically the magic numbers that are expected to never change, no matter how inconsistent the guest visible disk content is. Therefore, don't request BLK_PERM_CONSISTENT_READ. This allows to use format probing, e.g. in the context of 'qemu-img info', even while the guest visible data in the image is inconsistent during a running block job. Signed-off-by: Kevin Wolf --- block.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 6c8ef98dfa..68b724206d 100644 --- a/block.c +++ b/block.c @@ -2579,7 +2579,10 @@ static BlockDriverState *bdrv_open_inherit(const cha= r *filename, goto fail; } if (file_bs !=3D NULL) { - file =3D blk_new(BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL); + /* Not requesting BLK_PERM_CONSISTENT_READ because we're only + * looking at the header to guess the image format. This works= even + * in cases where a guest would not see a consistent state. */ + file =3D blk_new(0, BLK_PERM_ALL); blk_insert_bs(file, file_bs, &local_err); bdrv_unref(file_bs); if (local_err) { --=20 2.13.6