From nobody Tue Feb 10 09:25:03 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 1511277322580864.8571394883745; Tue, 21 Nov 2017 07:15:22 -0800 (PST) Received: from localhost ([::1]:35019 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eHAGK-0007bs-Qa for importer@patchew.org; Tue, 21 Nov 2017 10:15:00 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36893) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eHABz-00033z-TQ for qemu-devel@nongnu.org; Tue, 21 Nov 2017 10:10:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eHABy-0005AX-Sh for qemu-devel@nongnu.org; Tue, 21 Nov 2017 10:10:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48310) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eHABt-00057C-6K; Tue, 21 Nov 2017 10:10:25 -0500 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 mx1.redhat.com (Postfix) with ESMTPS id 5868DC053FD5; Tue, 21 Nov 2017 15:10:24 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-117-148.ams2.redhat.com [10.36.117.148]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1924F6C427; Tue, 21 Nov 2017 15:10:22 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Tue, 21 Nov 2017 16:10:11 +0100 Message-Id: <20171121151017.28158-2-kwolf@redhat.com> In-Reply-To: <20171121151017.28158-1-kwolf@redhat.com> References: <20171121151017.28158-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 21 Nov 2017 15:10:24 +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] [PULL 1/7] 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, peter.maydell@linaro.org, qemu-devel@nongnu.org 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 Reviewed-by: Fam Zheng --- 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