From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B177E606A321 for ; Wed, 28 Oct 2026 17:55:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=D1pJ0QYI Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xM7rI-0003Rp-Vb; Wed, 28 Oct 2026 13:54:44 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xM7rI-0003Ra-3r for qemu-devel@nongnu.org; Wed, 28 Oct 2026 13:54:44 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xM7rF-00081h-CH for qemu-devel@nongnu.org; Wed, 28 Oct 2026 13:54:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793210080; 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: in-reply-to:in-reply-to:references:references; bh=Y3SdHF9tPL2CGSziLCTtf1zhb8Dnq0Ef7aZQfrFKObo=; b=D1pJ0QYIJOpVz6c4SEUnEp83HhypIR4YsuB4/S50eoOjiDihkutGQ8fKlKlRuQKGGSiZ5q +dKk8sLDfvDze08xdfaPpvVklzJD7SZIpMlfsNAw2VYO9pnReA8IIQRAj98VUGNfGBH1V+ RhFvmmWjFYt7rVSfhz6ym5KYsyRllQQ= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-590-AyBVzPmJPPy1bNh-hQCrcA-1; Wed, 28 Oct 2026 13:54:37 -0400 X-MC-Unique: AyBVzPmJPPy1bNh-hQCrcA-1 X-Mimecast-MFC-AGG-ID: AyBVzPmJPPy1bNh-hQCrcA_1793210076 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 77071180267B; Wed, 28 Oct 2026 17:54:36 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5C3E51956087; Wed, 28 Oct 2026 17:54:34 +0000 (UTC) Date: Wed, 28 Oct 2026 12:54:31 -0500 From: Eric Blake To: Kevin Wolf Cc: qemu-block@nongnu.org, stefanha@redhat.com, afaria@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH 1/2] file-posix: Add 'accept-read-only-device' option Message-ID: References: <20261028171057.139326-1-kwolf@redhat.com> <20261028171057.139326-2-kwolf@redhat.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261028171057.139326-2-kwolf@redhat.com> User-Agent: NeoMutt/20260616 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Oct 28, 2026 at 06:10:56PM +0100, Kevin Wolf wrote: > The host_device block driver refuses to open a block device read-write > if the BLKROGET ioctl tells it that it's actually read-only. For such > devices it's possible to open a read-write file descriptor, but any > writes to the device would fail. > > There are valid use cases for which this check gets in the way, as > explained in the bug report: > > However, this behavior prevents a legitimate enterprise use case: > running VMs against storage replication target LUNs in a disaster > recovery configuration. Enterprise storage arrays (Dell Powermax, > Pure Storage) set the SCSI Write Protect bit on replication target > LUNs, causing the Linux kernel to mark them read-only via BLKROGET. > The VMs on the passive DR site need to start with these LUNs > attached - writes are expected to fail (the application middleware > knows it's on the passive side), and after a DR role swap the LUN > becomes writable and writes should succeed immediately without any > VM restart. > > In order to allow such use cases in which a currently read-only device > is deliberately opened read-write, add a new option to the host_device > driver that allows the user to skip the check. > > Buglink: https://redhat.atlassian.net/browse/RHEL-186136 > Signed-off-by: Kevin Wolf > --- > qapi/block-core.json | 19 ++++++++++++++++++- > block/file-posix.c | 23 ++++++++++++++++++++--- > 2 files changed, 38 insertions(+), 4 deletions(-) Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. 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